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© 2005 WebMD, Inc. All rights reserved.                                                        ACS Surgery: Principles and Practice
6 VASCULAR SYSTEM                                                                                  23 RENOVASCULAR DISEASE — 1



23 ENDOVASCULAR PROCEDURES
             FOR RENOVASCULAR DISEASE
Juan Ayerdi, M.D.,Matthew S.Edwards, M.D., and Kimberley J.Hansen, M.D., F.A.C.S.



The treatment of renovascular disease is currently in a state of evolu-     Contrast-Related Considerations
tion. Open surgical revascularization [see 6:22 Open Procedures for
                                                                             Patients with known renovascular disease typically have a high
Renovascular Disease] remains the gold standard, having demonstrat-
                                                                          prevalence of associated medical comorbidities (e.g., diabetes
ed its durability and efficacy in treating renovascular hypertension      mellitus, congestive heart failure, chronic renal insufficiency, and
and ischemic nephropathy; however, it is associated with substantial      diuretic-induced intravascular volume depletion). These condi-
morbidity and mortality, even when performed in centers with ex-          tions may necessitate alterations in the usual routines for patient
tensive experience.1-4 As a result, endovascular techniques for renal     preparation and use of iodinated contrast agents. Such agents are
revascularization, including percutaneous transluminal angioplasty        known to be capable of impairing excretory renal function,20
with or without endoluminal stent placement (PTAS), have emerged          sometimes permanently.The risk of this complication is highest in
as another option for the revascularization of occlusive renal artery     persons with preexisting dehydration,21 renal insufficiency,22-24 or
lesions. Compared with conventional open surgical revasculariza-          diabetes mellitus.25-27 Administration of higher volumes of iodi-
tion, these endovascular techniques offer a number of potential ben-      nated contrast material28,29 and use of high-osmolarity agents25-27
efits (e.g., decreased morbidity, lower mortality, shorter recovery       may also increase the risk of postprocedural renal function impair-
times, and reduced hospital resource utilization); however, they also     ment. Several reports, however, have demonstrated that peripro-
possess certain potential drawbacks (e.g., reduced effectiveness and      cedural administration of acetylcysteine30,31 and sodium bicar-
decreased durability).                                                    bonate hydration32 can lower the risk of renal function impair-
   Predictably, controversy persists regarding the appropriate            ment after angiography.
application of surgical and endovascular therapies to the treat-             In accordance with the available evidence, our current policy is to
ment of renovascular disease, with proponents of each modality            prepare all patients for aortorenal arteriography with saline hydra-
citing selected literature to support their position. In what follows,    tion (limited in patients with significant heart failure) and periproce-
we review key technical aspects of endovascular renal revascular-         dural administration of acetylcysteine, along with limited use of sodi-
ization and summarize the current data on technical results, clin-        um bicarbonate in patients who have preexisting renal insufficiency.
ical outcomes, and associated complications. There is reason to           Furthermore, we routinely select low-osmolarity iodinated contrast
believe that improvements in our ability to select patients most          agents in these patients and pay special attention to limiting the vol-
likely to benefit from treatment,5-10 as well as the emergence of         umes infused. In patients with moderate to severe preexisting renal
technical developments aimed at preventing procedure-related              insufficiency, carbon dioxide33,34 or gadopentate dimeglumine35 may
embolization11-13 and long-term restenosis,14 may be on the hori-         also be employed as an intra-arterial contrast agent to reduce or
zon. Such advances, if realized, may further narrow the gap               eliminate the use of iodinated contrast material. Our practice with
between the clinical results of surgical renal revascularization and      such patients is to use carbon dioxide or gadopentate dimeglumine
                                                                          for initial localization [see Figure 1a] and selective cannulation [see
those of its endovascular counterpart and may improve the mar-
                                                                          Figure 1b] of the renal artery, then to employ an iodinated contrast
ginal benefit and safety of renal artery PTAS.
                                                                          agent in small volumes for definitive planning and performance of
                                                                          the required intervention.
Preoperative Evaluation
                                                                            Technical Considerations
   The general principles of preoperative evaluation and patient
                                                                             Choice of arterial access route Femoral artery access,
selection for persons being considered for renal revascularization,       when feasible, is the most versatile and low-risk option. For non-
whether open or endovascular, will not be described in detail in          selective renal arteriography, either femoral artery provides ade-
this chapter. As a rule, our group reserves renal artery PTAS for         quate access. For selective renal cannulation, however, it is gener-
patients in whom open surgical repair is considered high risk or          ally better to use the femoral artery contralateral to the renal
who refuse such repair.                                                   artery being addressed; this approach takes advantage of the ten-
CONTRAST ARTERIOGRAPHY
                                                                          dency of the catheter to track preferentially toward the contralat-
                                                                          eral aortic wall and facilitates cannulation of the renal ostia.
   Despite advances in diagnostic imaging and functional testing             If the patient has downsloping renal arteries or if femoral access
that allow noninvasive identification of patients with renovascular       is not advisable, brachial artery access is a useful alternative. It is
disease,15-19 the formulation of an open surgical or endovascular         preferable to access the left brachial artery so as not to cross the
therapeutic plan continues to depend on visualization of the renal        origin of the right common carotid artery. Access may be estab-
artery anatomy by means of angiography. Accordingly, contrast             lished by means of either percutaneous or open techniques. The
arteriography of the renal arteries should be considered an inte-         risk of complications is higher with percutaneous brachial artery
gral component of the therapeutic armamentarium for clinically            access, and the maximum permissible sheath and catheter sizes
significant renal artery lesions.                                         are smaller.36 Accordingly, we generally use an open approach for
© 2005 WebMD, Inc. All rights reserved.                                                         ACS Surgery: Principles and Practice
6 VASCULAR SYSTEM                                                                                   23 RENOVASCULAR DISEASE — 2


             a                                                             b




             Figure 1 (a) Shown is bilateral high-grade renal artery stenosis visualized by using carbon dioxide angiogra-
             phy to localize the renal ostia. (b) Shown is selective right renal artery cannulation, with placement of a 6
             French left internal mammary artery (LIMA) guide catheter and selective renal arteriography using hand-
             injected half-strength iso-osmolar contrast material.


brachial artery access, with puncture, cannulation, and closure            eter have been gently advanced into the renal artery ostia, contrast
carried out under direct vision.                                           material is injected by hand to confirm intraluminal placement.
                                                                           Selective images are then obtained with low-volume power injection
   Choice of imaging views Aortography and selective renal                 or hand injection (our preference) of contrast material [see Figure 4].
arteriography with multiple projections are necessary for full radi-       The proximal third of the left renal artery usually courses anterior-
ographic evaluation of the renal arteries and the juxtarenal aorta.        ly, the middle third transversely, and the distal third posteriorly; the
Initial anteroposterior (AP) images of the visceral aorta are ob-
tained by delivering power contrast injections through a flush
catheter with multiple side holes positioned just beneath the
diaphragm at the level of the first lumbar vertebra.These initial AP
views provide an overview of the renal artery and the perivisceral
aortic anatomy [see Figure 2]. All further nonselective images of the
renal arteries should be obtained by moving the catheter to a loca-
tion below the origin of the superior mesenteric artery to prevent
contrast opacification of the visceral vessels, which could obscure
the anatomic details of the renal arteries.
   The renal arteries usually arise from the anterolateral or the
posterolateral aspect of the aorta. As a result, lesions within the
renal ostia often are not seen or appear insignificant on AP aor-
tograms. Oblique aortography or oblique selective renal arteriog-
raphy projects these portions of the vessel in profile and thus are
often better at identifying any renal ostial lesions present. As a rule,
the most useful projection for visualizing the renal ostia is a 15º to
30º left anterior oblique view, though other oblique views may also
be necessary.37,38 Previously obtained axial images of the renal ori-
gins (i.e., computed tomographic scans) may allow better estima-
tion of the necessary degree of obliquity and permit the use of
smaller amounts of iodinated contrast material and lower doses of
ionizing radiation [see Figure 3].
   For full delineation of lesions within the body of the renal artery,
selective arteriographic views may be required. Selective cannula-
tion is usually performed with an angled catheter (e.g., a cobra cath-
eter, a Sos catheter, or a renal double-curve catheter) in combina-
tion with a steerable guide wire; the varying configurations of the
available catheters offer specific advantages in particular anatomic       Figure 2 Anteroposterior (AP) aortogram is obtained by delivering
situations. Before selective renal artery cannulation, we typically        a power injection of iso-osmolar iodinated contrast material through
administer heparin intravenously. Once the guide wire and the cath-        a 5 French pigtail catheter positioned at the L1-2 interspace.
© 2005 WebMD, Inc. All rights reserved.                                                     ACS Surgery: Principles and Practice
6 VASCULAR SYSTEM                                                                              23 RENOVASCULAR DISEASE — 3


                                                                         Arteriographic Findings
                                                                          As noted (see above), the primary role for contrast arteriogra-
                                                                       phy in the treatment of renovascular disease is concerned with
                                                                       therapy rather than diagnosis. Angiography is most frequently per-
                                                                       formed to assess a renal artery lesion previously identified by
                                                                       means of renal duplex ultrasonography, CT arteriography, or
                                                                       magnetic resonance arteriography either before or as part of a
                                                                       therapeutic intervention. Most clinically significant renal artery
                                                                       lesions are caused by atherosclerotic disease or fibromuscular dys-
                                                                       plasia (FMD), with a small minority occurring secondary to other
                                                                       pathologic states. Each of these two major pathologic entities is
                                                                       associated with specific imaging characteristics and specific treat-
                                                                       ment considerations.

                                                                          Atherosclerotic renovascular disease Atherosclerosis of
                                                                       the renal artery accounts for roughly two thirds of all renovascular
                                                                       lesions. Elderly persons with multiple comorbid medical condi-
                                                                       tions and manifestations of atherosclerosis are most frequently
Figure 3 Axial CT scan image of the renal artery origins allows        affected.41-44 Atherosclerotic renal lesions generally represent a
estimation of the degree of obliquity required for optimal imaging     continuation of a process that begins in the aorta and spills over
of the renal ostia.                                                    into the origin of the renal vessels [see Figure 5]. These lesions are
                                                                       characterized by an eccentric, irregular narrowing of the ostium
                                                                       and the proximal portion of the renal artery [see Figure 6]. In the
                                                                       majority of cases, the lesions are limited to the ostia and the prox-
                                                                       imal renal artery, and the two sides are affected equally.45 The aor-
                                                                       tic origin of the lesion has important implications for treatment.
                                                                       Placement of an endovascular stent into the proximal renal artery,
                                                                       without the aortic origin of the plaque being taken into account,
                                                                       may result in residual or recurrent disease. Occlusions of the renal
                                                                       artery are also common in patients with clinically significant
                                                                       lesions [see Figure 7] and frequently occur in the setting of con-
                                                                       tralateral renal artery stenosis.2,3

                                                                          Fibromuscular dysplasia FMD is a term used to describe
                                                                       a group of histologically distinct pathologic conditions of the arte-
                                                                       rial wall that most commonly affect the main renal artery and its
                                                                       branches. FMD of the renal artery, with resultant renal artery
                                                                       stenosis, is responsible for approximately 25% to 30% of treated
                                                                       cases of renovascular hypertension.45 The lesions are usually cate-
                                                                       gorized according to the layer of the arterial wall predominantly
Figure 4 Shown is selective arteriography of the right renal
artery using hand-injected iso-osmolar contrast material through
a complexly curved Simmons catheter.


right renal artery generally pursues a more consistent posterior
course. For full delineation of lesions in the various segments,
oblique and cranial-caudad rotated images may be necessary.

   Adjunctive measures The performance of arteriographic
imaging of the renal arteries also affords the surgeon the opportu-
nity to employ other measures to characterize a renal artery lesion.
For example, the hemodynamic effects of angiographically detect-
ed stenosis or the treatment thereof can be assessed by making
direct pressure measurements proximal and distal to the lesion. In
general, we consider any pressure gradient greater than 10 mm Hg
to be indicative of hemodynamically significant renovascular dis-
ease. Additional anatomic information can be obtained by means
of intravascular ultrasonography of the renal artery, which can
provide detailed information on plaque morphology, vessel size,
and potential dissection flaps to complement the data obtained         Figure 5 Aortic endarterectomy specimen demonstrates the
through arteriography.39,40                                            pathologic basis of atherosclerotic renovascular disease.
© 2005 WebMD, Inc. All rights reserved.                                                    ACS Surgery: Principles and Practice
6 VASCULAR SYSTEM                                                                              23 RENOVASCULAR DISEASE — 4

                                                                       beads [see Figure 8], an appearance created by weblike stenotic
                                                                       areas with intervening areas of poststenotic dilatation. These
                                                                       lesions are frequently unilateral, and they can also produce a renal
                                                                       artery aneurysm or dissection.47 Stenotic medial fibroplasia of the
                                                                       main renal artery is among the lesions most amenable to endovas-
                                                                       cular treatment. In our view, however, the presence of branch ves-
                                                                       sel disease or aneurysms precludes such treatment.
                                                                          Perimedial dysplasia accounts for approximately 15% of cases
                                                                       of FMD and is most commonly manifested by the appearance of
                                                                       multiple irregular stenoses without microaneurysms.46 Intimal
                                                                       fibroplasia is the least common variant of FMD, representing
                                                                       fewer than 5% of recognized cases, and the typical lesions are
                                                                       smooth concentric stenoses.45,46 In general, perimedial dysplasia
                                                                       and intimal fibroplasia tend to respond less well to endovascular
                                                                       treatment than medial fibroplasia does.


                                                                       Operative Planning

                                                                       PATIENT PREPARATION

                                                                          Patient preparation for renal artery PTAS is similar to that rou-
                                                                       tinely carried out for diagnostic arteriography. Oral intake of food
                                                                       and liquid is stopped at midnight the evening before the procedure.
Figure 6 Magnified preintervention aortogram demonstrates              Warfarin is discontinued at least 4 days beforehand; aspirin and
ostial right renal artery atherosclerotic stenosis.                    clopidogrel are continued. Intravenous fluids and acetylcysteine are
                                                                       administered the evening before the procedure, with care taken to
involved—hence the terms medial fibroplasia, perimedial dyspla-        avoid fluid overload in patients with impaired cardiac function. Rou-
sia, and intimal fibroplasia. Medial fibroplasia is the most com-      tine medications, with the exception of angiotensin-converting en-
mon variant, representing 85% of recognized cases. It is encoun-       zyme inhibitors and angiotensin receptor antagonists, are taken on
tered almost exclusively in women, most commonly in the third or       the morning of the procedure with a sip of water. A first-generation
fourth decade of life.45,46 The arteriographic pattern most fre-       cephalosporin is administered intravenously 30 minutes before the
quently associated with medial fibroplasia resembles a string of       procedure unless the patient is allergic.
                                                                          After the intervention, the patient is observed in the hospital
                                                                       overnight to check for access-site problems and severe alterations
                                                                       in blood pressure. Acetylcysteine is continued throughout the hos-
                                                                       pital stay, and oral administration of clopidogrel is initiated the
                                                                       evening after the procedure. The patient continues to take clopi-
                                                                       dogrel for at least 30 days after revascularization and remains on
                                                                       aspirin therapy indefinitely.
                                                                       CORRELATION OF DIAGNOSTIC IMAGES WITH
                                                                       CLINICAL FINDINGS

                                                                          Once the diagnostic portion of the procedure is completed, the
                                                                       images obtained are closely examined and correlated with the
                                                                       patient’s clinical presentation. Intra-arterial pressure measure-
                                                                       ments are occasionally misleading in renal vessels. Because most
                                                                       renal arteries are approximately 5 to 6 mm in diameter, a stenotic
                                                                       lesion that causes a greater than 60% reduction in the luminal
                                                                       diameter leaves only 2.0 to 2.5 mm of patent lumen. A 4 or 5
                                                                       French diagnostic catheter may completely occlude this narrowed
                                                                       lumen, thus resulting in an inaccurately low pressure measure-
                                                                       ment distal to the stenosis. Accordingly, it is our practice to assess
                                                                       the anatomic arteriographic information in the light of the func-
                                                                       tional significance of the lesion as determined by either renal vein
                                                                       renin assays or duplex ultrasonography.
                                                                       MATERIALS AND INSTRUMENTS

                                                                         The materials commonly used for renal artery PTAS at our
                                                                       center include various guide wires, catheters, sheaths, balloons,
                                                                       and stents [see Table 1]. The basic principles underlying the use of
Figure 7 Aortogram demonstrates right renal artery stenosis and        these devices are outlined more fully elsewhere [see 6:8 Fun-
left renal artery occlusion with distal renal artery reconstitution.   damentals of Endovascular Surgery].
© 2005 WebMD, Inc. All rights reserved.                                                                      ACS Surgery: Principles and Practice
6 VASCULAR SYSTEM                                                                                               23 RENOVASCULAR DISEASE — 5

                                                                                        ter and the introducer sheath are exchanged over a 0.035 in. guide
                                                                                        wire so that an access platform can be established that will provide
                                                                                        secure renal artery access for the therapeutic intervention.
                                                                                           Most angioplasty and stenting devices in current use will pass
                                                                                        through a 6 French lumen. Access options include guide sheaths
                                                                                        and guide catheters. Common to both of these options is the pro-
                                                                                        vision of a long mechanical support segment for guide-wire place-
                                                                                        ment that affords direct access to the renal artery for easy passage
                                                                                        of therapeutic devices to the target lesion [see Figure 9]. Such sys-
                                                                                        tems vary in shape and diameter and come in multiple configura-
                                                                                        tions to facilitate renal artery access in different situations.
                                                                                           After the tip of the guide catheter is positioned at or within the
                                                                                        renal artery orifice, guide-wire access across the lesion is obtained.
                                                                                        For all subsequent manipulations, the sheath or the guide catheter
                                                                                        should not be advanced beyond the orifice, because the nonta-
                                                                                        pered tip may injure the vessel. Depending on the type, severity,
                                                                                        and location of the lesion, a 0.35, 0.18, or 0.14 in. guide wire with
                                                                                        a floppy radiopaque tip is chosen.The smaller guide-wire systems
                                                                                        appear to have inherent advantages, in terms of ability to cross
Figure 8 Selective right renal arteriogram demonstrates findings                        tighter stenoses, limitation of renal artery trauma, and liberation of
indicative of medial fibroplasia.                                                       emboli, but whether these apparent advantages are real remains to
                                                                                        be proved. Once the guide wire is in place, the access platform is
                                                                                        secured and remains in place until the intervention and any
Operative Technique                                                                     postintervention imaging are complete.
STEP 1: SECURING OF ACCESS TO RENAL ARTERY FOR                                          STEP 2: TRANSLUMINAL ANGIOPLASTY
THERAPEUTIC INTERVENTION
                                                                                           With the guide wire secured distal to the lesion, therapeutic
   Once the decision for endovascular intervention is made, the pa-                     intervention may proceed. Both coaxial systems (in which the
tient is systemically heparinized, and the 5 French diagnostic cathe-                   entire catheter is exchanged over the wire, so that an assistant is

                                                  Table 1         Standard Equipment for Renal PTAS
             Device Category                    Type                           Proprietary Name                      Length              Diameter

                                      Initial                      Starter 3 mm J                            180 cm               0.035 in.

                                                                   Magic Torque                              180 cm               0.035 in.
                Guide wires
                                      Selective                    Platinum Plus, V-18                       145–180 cm           0.018 in.
                                                                   Transend, GuardWire                       165–200 cm           0.014 in.

                                      Flush angiography            Pigtail                                   70 cm                5 Fr

                                                                   Cobra C1 or C2                            65 cm                5 Fr
                                      Selective: diagnostic        Contra 2                                  65 cm                5 Fr
                                                                   VS–1 or Sos                               65 cm                5 Fr
                                                                   Simmons                                   65 cm                5 Fr

                  Catheters                                        Renal Double Curve                        55 cm                6 Fr
                                                                   LIMA                                      55 cm                6 Fr
                                      Selective: guide
                                                                   JR 4                                      55 cm                6 Fr
                                                                   Hockey Stick                              55 cm                6 Fr

                                      Pressure-measuring           Straight Glide                            90 cm                4 Fr

                                      Initial access                                                         10 cm                5 Fr

                  Sheaths             Therapeutic access                                                     10 cm                6 Fr

                                                                   Pinnacle Destination                      45 cm                6 Fr
                                      Selective: guide
                                                                   Flexor Check Flow ANL2                    45 cm                6 Fr

                                                                                                             1.5–2.0 cm balloon   3 mm balloon
                                      Predilation                  Savoy, Gazelle, Aviator, Symmetry
                                                                                                             75–90 cm shaft       5 Fr sheath
            Angioplasty balloons
                                                                                                             1.5–2.0 cm balloon   4–7 mm balloon
                                      Therapeutic                  Savoy, Gazelle, Aviator, Symmetry
                                                                                                             75–90 cm shaft       5 Fr sheath

                                                                                                             12–29 mm stent       5–7 mm stent
                   Stents*            Balloon-expandable           Genesis, Express, Racer
                                                                                                             75–90 cm shaft       6 Fr sheath
           *None of these stents are FDA-approved for use in renal arteries.
© 2005 WebMD, Inc. All rights reserved.                                                            ACS Surgery: Principles and Practice
6 VASCULAR SYSTEM                                                                                      23 RENOVASCULAR DISEASE — 6


      a




      b




                                                                                                    Figure 9 Shown are (a) a guide catheter
                                                                                                    inserted through a short 6 French arteri-
                                                                                                    al sheath and (b) a diagnostic catheter
                                                                                                    inserted through a guide sheath.


required to control the wire during intervention and catheter                 STEP 3: ENDOLUMINAL STENTING
exchange) and monorail or rapid-exchange systems (in which only                  Endovascular stent placement may be performed either as a pri-
the distal portion of the catheter is over the wire, so that a single         mary procedure or as a secondary procedure in response to sub-
operator can control the wire during intervention and catheter                optimal results from angioplasty. Most FMD lesions and nonos-
exchange) are available for renal artery intervention.                        tial atherosclerotic lesions respond well to angioplasty alone.
   Regardless of the system chosen, the principles of intervention            Secondary stent placement should, however, be considered for
remain the same. Transluminal angioplasty of the renal artery                 nonostial lesions that do not respond appropriately to angioplasty.
may be performed either as the sole therapy for a renal artery                Secondary stent placement is typically performed to address elas-
lesion or as a means of predilating a lesion so that an endolumi-             tic recoil, residual stenosis (> 30%), pressure gradients (> 10 mm
nal stent can be placed. Angioplasty may also be employed to                  Hg), and myointimal flaps or dissections. Either balloon-expand-
treat recurrent renal artery stenoses after surgical or endovascu-            able or, less commonly, self-expanding stents may be employed in
lar therapy. Angioplasty is an effective stand-alone therapy in               the renal artery. Typically, balloon-expandable stents have greater
most cases of main renal artery disease (FMD and nonostial ath-               radial strength and can be placed more precisely, whereas self-
erosclerosis) but is frequently ineffective for atherosclerotic ostial        expanding stents are more flexible and conform more readily to
and proximal renal artery disease.                                            the shape of the lumen.We employ balloon-expandable stents pri-
   The angioplasty balloon size is chosen on the basis of quantita-           marily in the treatment of ostial atherosclerotic lesions, where their
tive angiographic images. Direct cut-film images with ball-bearing            advantages are particularly useful.
or marker-catheter reference points may be used, as may the quan-                In general, the technical aspects of stent placement parallel
titative software packages available on most contemporary digital             those of transluminal angioplasty. Frequent hand injections of
angiographic systems. In general, the angioplasty balloon should              small amounts of contrast material through the guide sheath or
be slightly larger than the adjacent normal artery for primary                catheter are employed to guide the stent into position across the
treatment and somewhat smaller for predilation of a stenotic                  lesion before deployment [see Figure 10]. After the stent has been
lesion. For predilation before endoluminal stent placement, we                deployed, a completion angiogram is performed while guide-wire
usually employ a 3 × 20 mm low-profile angioplasty balloon.This               access to the renal artery is maintained. This is accomplished by
choice tends to make stent passage less traumatic and helps in esti-          hand injection of contrast through the guide sheath or catheter.
mating the stent diameter and length required.                                For the treatment of ostial or proximal renal artery lesions, it is
   During inflation of the angioplasty balloon, the aortic origin of          preferable to position the stent with 1 to 2 mm extension into the
most ostial plaques is indicated by the appearance of a visible               aorta. Frequent hand injection of contrast material through the
“waist,” and the image can be centered over a bony landmark to                guide sheath allows precise placement of the stent and helps pre-
facilitate subsequent stent placement. It is not unusual for the              vent misdeployment. If the stent is placed too far into the artery,
patient to experience some discomfort during balloon inflation.               the true renal orifice is not supported, and there is a greater
This discomfort should resolve quickly when the balloon is deflat-            chance of residual or recurrent disease.48-52 Such recurrent disease
ed; if it does not, renal artery trauma should be suspected. It is our        often does not respond to further endovascular attempts; accord-
practice to inflate the balloon slowly to its fully inflated profile at the   ingly, it is advisable to use the shortest possible stent that will ade-
rated nominal pressure, then maintain inflation for 30 to 45 sec-             quately support the lesion. In addition, a stent that extends well
onds before deflation.                                                        out into the distal renal artery can make later surgical options
   Once the balloon has been completely deflated, it is removed,              more difficult53 and typically carries a higher failure rate.
and selective angiography is repeated to assess the response of the              A balloon-expandable stent is deployed by inflating the angio-
lesion to angioplasty and check for complications. Guide-wire                 plasty balloon on which it is mounted. In the past, these stents had
access must be maintained until the end of the procedure so that              to be crimped and hand-mounted on the angioplasty balloon,
complications or unsatisfactory results (e.g., dissection or residual         which made their delivery somewhat insecure. Currently available
stenosis) can be addressed.                                                   stents, however, come securely premounted on low-profile deliv-
© 2005 WebMD, Inc. All rights reserved.                                                       ACS Surgery: Principles and Practice
6 VASCULAR SYSTEM                                                                                 23 RENOVASCULAR DISEASE — 7


ery systems capable of passing across most lesions with minimal         Postoperative Care
or no predilation. We deploy these stents with 1 to 2 mm exten-            Longitudinal follow-up of all patients undergoing renal revas-
sion into the aorta, guided by anatomic information provided by         cularization is mandatory to check for recurrent disease, con-
previous positioning over bony landmarks. Self-expanding stents,
                                                                        tralateral disease, and deterioration of clinical benefit, as well as
though not commonly applied to the treatment of renovascular
                                                                        other preventable cardiovascular and peripheral vascular condi-
disease, can also be employed in this setting. These devices are
                                                                        tions. Our current approach to follow-up entails clinical visits at 1,
deployed by retracting an outer membrane of the delivery device
                                                                        3, 6, 9, 12, 18, and 24 months after renal artery PTAS, with renal
to expose the stent. Care must be taken during deployment to
                                                                        duplex ultrasonography, blood pressure measurement, and serum
ensure that foreshortening of the stent does not compromise cov-
erage of the lesion.                                                    creatinine measurement at each visit. After 24 months, this inten-
   After a stent is deployed, there may be residual narrow areas        sive early follow-up is relaxed to a yearly visit schedule if no con-
within the stent that necessitate balloon dilatation. These areas       ditions necessitating shorter visit intervals have been identified.
may be visible on fluoroscopic evaluation of the stent, or they may        Recurrent disease after renal stenting is a significant concern, and
be detected during postdeployment selective renal angiography.          disease that recurs within the stent itself can be a particularly chal-
   After all therapeutic measures have been completed, the tech-        lenging problem [see Figure 11a]. Because most such recurrences are
nical result is assessed and undetected defects sought by means of      related to intimal hyperplasia, repeat balloon angioplasty generally
repeat pressure-gradient measurements, intravascular ultrasonog-        does little to improve the situation. Initial dilatation with a Cutting
raphy, or both. When a satisfactory result is obtained, the guide       Balloon (Boston Scientific, Natick, Massachusetts) is extremely use-
wire and the sheath are removed and hemostasis is secured.              ful for releasing the fibrous scar tissue of the restenotic lesion and al-
Although it is possible to perform bilateral renal interventions in a   lowing subsequent dilatation to a larger diameter with a convention-
single procedure, we prefer, when possible, to stage these inter-       al angioplasty balloon.The Cutting Balloon consists of a noncompliant
ventions so as to minimize contrast loads.                              balloon with three or four atherotomes (microsurgical blades) mount-


               a                                                        b




               c
                                                                        Figure 10 (a) The orifice of a right renal artery
                                                                        with high-grade ostial stenosis is catheterized
                                                                        with a 6 French cobra catheter, and the lesion is
                                                                        crossed with a 0.014 in. guide wire. (b) A balloon-
                                                                        mounted stent is positioned across the renal
                                                                        artery stenosis with the help of intermittent con-
                                                                        trast injections and bony landmarks. (c) A fully
                                                                        expanded stent is positioned in the renal artery.
© 2005 WebMD, Inc. All rights reserved.                                                         ACS Surgery: Principles and Practice
6 VASCULAR SYSTEM                                                                                  23 RENOVASCULAR DISEASE — 8


               a                                                            b




               c
                                                                            Figure 11 (a) Shown is high-grade recurrent in-
                                                                            stent restenosis of the right renal artery. (b) The
                                                                            Cutting Balloon is useful in dealing with such
                                                                            lesions. (c) Dilation with a 4 × 15 mm Cutting
                                                                            Balloon is followed by dilation with a standard 6 × 20
                                                                            mm angioplasty balloon, and a completion
                                                                            angiogram is obtained.




ed longitudinally on its outer surface [see Figure 11b].When the device     fusion, surgical intervention, and deep vein thrombosis.There was
is inflated, the atherotomes score the intimal hyperplasia within the       no apparent association between pretreatment patient characteris-
stent; the balloon is then rotated and reinflated to score the lesion in    tics and the subsequent incidence of major complications. Two
multiple planes.To date, this technique has been used primarily in          patients (1.1%) died within 30 days after the procedure.
coronary arteries, but it has also been applied to the treatment of renal
artery in-stent restenosis.54 After the lesion has been scored, a larger    Outcome Evaluation
balloon is inserted and inflated to redilate the lesion [see Figure 11c].
                                                                               To be considered successful, renal artery revascularization
                                                                            should (1) improve quality of life, (2) reduce the incidence of
Complications                                                               adverse cardiovascular disease events, (3) slow or halt the pro-
                                                                            gression of chronic renal insufficiency, (4) lower the incidence
   Complications can arise at any point during renal artery PTAS or
                                                                            of dialysis-dependent renal failure, and (5) improve overall sur-
during the early postoperative period. Potential complications in-
                                                                            vival. Unfortunately, few studies addressing these clinical out-
clude access-site complications (e.g., hematoma, pseudoaneurysm,
                                                                            come measures have been performed or reported. Thus, the
retroperitoneal hemorrhage, arteriovenous fistula, and closure-device
                                                                            outcome of renal revascularization is currently assessed on the
infection), contrast-mediated allergic reactions or nephrotoxicity,         basis of (1) the extent to which the procedure is anatomically or
atheroembolism, and direct renovascular trauma. In a meta-analysis          technically successful and (2) the degree to which the proce-
published in 2000, the reported complication rate after renal PTAS          dure alleviates or cures associated hypertension and ischemic
ranged from 0% to 40% (mean rate, 11%).55 The most frequently               nephropathy. Technical success and the response of hyperten-
reported complications were hematomas at arterial access sites.             sion or renal dysfunction to therapy are assumed to be the
Severe complications occurred in 9% of patients and included renal          mechanisms by which the five important clinical outcomes list-
failure, segmental renal infarction, perinephric hematoma, and renal        ed are achieved.
artery thrombosis.The mean mortality was 1%.                                   Interpretation of the results of renal artery PTAS as reported in
   A large single-center retrospective review of complications after        the current literature is challenging. Despite the publication of
endovascular treatment with renal artery stenting reported similar          hundreds of reports on this procedure, it remains unclear how
results.56 Major complications occurred after 15 of 179 procedures          renal artery PTAS compares with surgical renal revascularization
(8.4%) and included renal infarction, permanently increased                 and whether renal artery PTAS conveys any meaningful benefit to
serum creatinine concentration, dialysis dependence, blood trans-           patients beyond what can be achieved with medical therapy alone.
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6 VASCULAR SYSTEM                                                                                         23 RENOVASCULAR DISEASE — 9


                          Table 2—Results after Primary Percutaneous Transluminal Angioplasty for
                                           Atherosclerotic Renal Artery Stenosis

                                            Patients with   Renal Function Response (%) Hypertension Response (%)              Major
                         Patients Technical    Renal                                                              Restenosis Complication
        Study              (N)    Success Dysfunction                                                              Rate (%)
                                                          Improved Unchanged Worsened Cured Improved Failed                   Rate (%)
                                  Rate (%)       (N)

Canzanello (1989)60        100         73            66             52                    48              59           41        19           20

Klinge (1989)62            134         78            NR                     NR                     11          78      10        16           11

Baert (1990)58             165         83            NR                     NR                     32          36      32        10           11

Weibull (1993)67           29          83            NR      21             75            4        13          71      17        25           17

Losinno (1994)64           153         95            59      27             67            6        12          51      37        NR            8

Bonelli (1995)59           190         82            NR           No change in mean SCr             8          62      30        10           23

Hoffman (1998)61           50          58            36      44             23            33        3          64      32        27           14

Klow (1998)63              295         92            NR           No change in mean SCr             5          59      31        40            8

Zuccala* (1998)68          99          92            33      39             50            11       18          44      48        17            8

Paulsen (1999)69           135         90            79      23             56            21        6          41      53        45            9

Van de Ven (1999)65        41          57            22      18             55            27        5          44      51        48           29

Baumgartner (2000)70       163         95            107     33             42            25              43           57        35            3

Van Jaarsveld (2000)66     56          91            NR           No change in mean SCr             7          61      32        48            5

Total                     1,610        86            402     32             51            17       11          54      35        25           12

*All diabetic patients.
NR—not reported SCr—serum creatinine concentration



These shortcomings in our understanding of renal artery PTAS                     HYPERTENSION RESPONSE
(and of surgical renal revascularization, for that matter) stem                     Three randomized, controlled studies have compared endovas-
largely from the lack of well-designed clinical trials investigating             cular surgery with medical treatment of renovascular hyperten-
these questions. Such trials will ultimately be necessary to estab-              sion. These studies provide the best available data on the efficacy
lish the utility and safety of renal artery PTAS in the treatment of             of endovascular therapy for managing hypertension, but they are
renovascular disease. Until such trials are performed, interpreta-               limited in that they all investigated the use of renal artery angio-
tion of the existing literature is the only available guide to the pru-          plasty without primary stent placement. The first study involved
dent application of renal artery PTAS.                                           49 patients with unilateral renal artery stenosis who were ran-
TECHNICAL SUCCESS                                                                domly assigned to either angioplasty or best medical hypertension
                                                                                 treatment.90 The angioplasty group demonstrated no statistically
   Technical success is defined on the basis of angiographic find-
                                                                                 significant decrease in blood pressure; however, it did demonstrate
ings at the completion of renal artery PTAS. Criteria include com-
                                                                                 improvement in hypertension control, as evidenced by a signifi-
plete stent coverage of the targeted lesion (if a stent was used) and
                                                                                 cant reduction in the amount of antihypertensive medications
residual diameter-reducing stenosis of less than 30%.57 Angio-
plasty as stand-alone treatment of renovascular disease is of limit-             required. The second study, reported by the Scottish and
ed applicability, especially in cases of atherosclerotic disease of the          Newcastle Renal Artery Stenosis Collaborative Group, involved
renal ostia (the most commonly encountered lesion). The reason                   55 patients who were randomly assigned to either angioplasty or
is that ostial renovascular disease usually represents the extension             best medical antihypertensive therapy.91 Patients with both unilat-
of aortic-based plaque, which possesses substantial inherent recoil              eral and bilateral renal artery stenosis were included in this study.
and thus is resistant to dilatation unless mechanical support is                 There was a modest improvement in blood pressure control in the
added to help maintain the enlarged lumen.                                       angioplasty group, but this benefit was confined to those patients
   A review of the literature on renal artery angioplasty for ath-               who had bilateral disease. None of the patients were cured of their
erosclerotic renovascular disease determined that immediate tech-                hypertension. The third study—the largest prospective, random-
nical success was reported in 86% of cases [see Table 2].58-70 The               ized trial reported to date in this area—was performed by the
immediate technical success rate was higher when a stent was                     Dutch Renal Artery Stenosis Intervention Cooperative Study
employed, especially in cases of ostial disease. A review of the lit-            Group.66 A total of 106 patients were randomly assigned to either
erature on primary stenting for atherosclerotic renovascular dis-                renal artery angioplasty or best medical therapy for renovascular
ease determined that primary use of stents yielded an immediate                  hypertension. At 12 months, there was no significant reduction in
technical success rate of 98% [see Table 3].5,48,50,51,65,70-89 The supe-        either systolic or diastolic blood pressure, though multiple treat-
riority of primary stenting for ostial lesions was confirmed in a                ment crossovers occurred that might have skewed the results
prospective clinical trial.65                                                    toward the best medical therapy arm.The authors concluded that
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6 VASCULAR SYSTEM                                                                                              23 RENOVASCULAR DISEASE — 10


                                             Table 3—Results after Primary Arterial Stent Placement for
                                                      Atherosclerotic Renal Artery Stenosis

                                                     Patients with   Renal Function Response (%) Hypertension Response (%)              Major
             Study                Patients Technical    Renal                                                              Restenosis Complication
                                           Success Dysfunction                                                              Rate (%)   Rate (%)
                                    (N)                            Improved Unchanged Worsened Cured Improved Failed
                                           Rate (%)       (N)

 Rees (1991)84                      28         96            14    36           36              29        11        5         36         39           18

 Kuhn     (1991)81                   8         92            NR                  NR                       22        34        44         17           13

 Joffre   (1992)80                  11         91             4    50           50              0         27        64         9         18           13

 Hennequin     (1994)77             15        100             6    20           40              40        7         93         0         27           19

 Macleod     (1995)83               28        100            16    25                   75                0         40        60         17           19

 Van de Ven     (1995)88            24        100            NR    33           58              8         0         73        27         13           13

 Dorros    (1995)72                 76        100            29    28           28              45        6         46        48         25           11

 Henry    (1996)51                  55        100            10    20                   80                18        57        24          9            3

 Iannone     (1996)79               63         99            29    36           46              18        4         35        61         14           32

 Harden     (1997)76                32        100            32    35           35              29                  NR                   13           19

 Blum     (1997)48                  68        100            20     0          100              0         16        62        22         17            0

 Boisclair   (1997)50               33        100            17    41           35              24        6         61        33          0           21

 Rundback      (1998)86             45         94            45    18           53              30                  NR                   26            9

 Fiala   (1998)5                    21         95             9     0          100              0              53             47         65           19

 Dorros    (1998)73                 163        99            63         No change in mean SCr             1         42        57         NR           14

 Tuttle   (1998)87                  120        98            74    16           75              9         2         46        52         14            4

 Gross    (1998)75                  30        100            12    55           27              18        0         69        31         13           NR

 Henry    (1999)78                  200        99            48    29           67              2         19        61        20         11            2

 Rodriguez-Lopez       (1999)85     108        98            32         No change in mean SCr             13        55        32         26           12

 Van de Ven     (1999)65            40         88            29    17           55              28        15        43        42         14           30

 Baumgartner       (2000)70         64         95            NR    33           42              25             43             57         28            9

 Giroux    (2000)74                 30         95            21           76                    24             53             47         NR           NR

 Lederman      (2001)82             300       100            111    8           78              14             70             30         21            2

 Bush     (2001)71                  73         89            50    23           51              26                  NR                   NR            9

 Zeller   (2004)89                  456        98            239   34           39              27             46             54         NR           NR

 Total                             2,091       98            910   22           56              22        10        51        39         19            9

NR—not reported         SCr—serum creatinine concentration



angioplasty had little advantage over antihypertensive therapy in                        To date, only one prospective, randomized, controlled study has
the treatment of renovascular hypertension.                                           compared endovascular treatment with surgical revascularization for
   A 2000 meta-analysis examined data from retrospective reports                      the treatment of renovascular hypertension.67 In this report, 58
describing a total of 1,322 patients who were treated with renal                      patients with renovascular hypertension were randomly assigned to
artery angioplasty or stenting.55 The overall hypertension cure rate                  either surgical revascularization or angioplasty. In both groups, hyper-
was 20%, and 49% of the patients had improved blood pressure                          tension was cured or improved in approximately 90% of patients.
control. In a similar review of data from 36 reports on primary                       However, more than half of the patients in whom angioplasty failed
renal angioplasty or stent placement for the treatment of athero-                     were switched to the surgical arm for revascularization. On the basis
sclerotic renal artery stenosis [see Tables 2 and 3], the reported                    of these results, the authors recommended angioplasty as the treat-
treatment indications included hypertension, renal insufficiency,                     ment of choice for selected renovascular lesions contributing to reno-
and a combination of the two.The percentage of patients cured of                      vascular hypertension, with aggressive follow-up and repeat interven-
hypertension ranged from 0% to 32% (mean, 10%), and the per-                          tion (endovascular and surgical) carried out as needed.
centage of patients experiencing improved blood pressure control                         Another group of investigators, however, reported that the ben-
ranged from 5% to 93% (mean, 53%).                                                    eficial blood pressure response seen after open surgical repair for
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6 VASCULAR SYSTEM                                                                              23 RENOVASCULAR DISEASE — 11


failed angioplasty may be less than that seen in patients who           55%.2-4 Furthermore, patients with ischemic nephropathy whose
undergo primary surgical repair without previous endovascular           renal function did not change after surgical revascularization had
treatment.53 Moreover, a previous endovascular procedure may            increased rates of death and dialysis dependence during follow-up
make open surgical repair technically more demanding, especially        that were similar to those noted in patients with poorer renal func-
if an endoluminal stent is present.                                     tion after revascularization.2,3 These findings raise serious ques-
    At present, there are no level I data demonstrating any associ-     tions about the concept of stabilized renal function and suggest
ation between improved hypertension control after renal artery          that improved postprocedural renal function may be the most per-
PTAS and either increased survival or reduced morbidity and             tinent surrogate outcome marker for predicting improved survival
mortality from adverse cardiovascular events. In fact, very few         and dialysis independence.
reports contain any data on these important clinical outcomes,
                                                                        LONG-TERM COMPLICATIONS
and those that do have not documented any significant differ-
ences between medical management and renal artery                          Complications and suboptimal outcomes may also develop in a
PTAS.66,90,91 There is some evidence in the surgical literature of      delayed manner. The principal long-term complications include
associations between hypertension response and a decrease in            restenosis of the renal artery and inadequate durability of clinical
adverse cardiovascular events; notably, however, these associa-         benefit. Restenosis is a common occurrence with all catheter-based
tions appear to exist only for persons whose renovascular hyper-        methods of revascularization. According to the meta-analysis cited
tension is cured.2                                                      earlier,55 restenosis complicates 11% to 42% (mean, 26%) of renal
                                                                        artery angioplasties and 12% to 23% (mean, 17%) of renal artery
RENAL FUNCTION RESPONSE
                                                                        stent procedures. Other studies have yielded very similar results [see
   Several factors hinder accurate assessment of the effect of renal    Tables 2 and 3]. Restenosis may or may not be clinically significant.
artery PTAS on renal function.To date, no prospective, controlled       Accordingly, the decision whether to treat restenotic lesions should
studies have compared renal function responses after medical,           be made on the basis of the specific physiologic or clinical findings,
surgical, and endovascular treatment of renal artery stenosis.          not simply because restenosis is present.
Most observational series report results from a diverse group of           The beneficial clinical responses noted after renal artery PTAS
patients whose baseline renal function and subsequent responses         frequently are not durable. In two studies that reported on a to-
to treatment vary widely. Interpretation of the existing renal func-    tal of 222 individuals undergoing renal artery PTAS, the investiga-
tion response data is further complicated by the insensitivity of se-   tors found that the clinical response, especially the renal func-
rum creatinine measurement (the most commonly employed in-              tion response, was transient.92,93 Overall, at 5 years, 50% to 70%
dicator of renal function in these studies) to changes in renal         of patients exhibiting a positive hypertension response and
function, especially in patients with serum creatinine levels lower     fewer than 50% of those exhibiting a positive renal function
than 1.2 mg/dl.                                                         response (defined as improvement or stabilization) retained any
   These limitations notwithstanding, a number of reports pub-          benefit. This deterioration of clinical benefit occurred even
lished between 1989 and 2004 provided useful data on renal func-        though a patent renal artery was maintained in all cases. Such
tion response after renal artery PTAS, expressed in terms of            results stand in stark contrast to the documented durability of the
change (or lack of change) in serum creatinine concentration [see       clinical response after surgical revascularization and underscore the
Tables 2 and 3]. With improvement defined as a 20% or greater           need for close lifelong follow-up of all patients undergoing renal
decrease in serum creatinine concentration, response rates ranging      revascularization.1-4
from 0% to 55% were observed (mean, 22%). These results are
                                                                        OUTCOMES AFTER RENAL ARTERY PTAS FOR FMD
very similar to those reported in the 2000 meta-analysis cited ear-
lier (range, 0% to 50%; mean response rate, 30%).55 A number of            Patients with FMD respond to renal artery PTAS much dif-
authorities also make use of the concept of “stabilized” renal func-    ferently from those with renal artery atherosclerosis. FMD is
tion, defined as a less than 20% change in serum creatinine con-        most commonly manifested as medial fibroplasia in a young
centration. By this definition, renal function was stabilized in the    woman. In general, balloon angioplasty appears to be an
majority of patients included in the studies published between          acceptable treatment for adult patients with such lesions, and
1989 and 2004 (range, 23% to 100%; mean response rate, 53%)             this approach yields excellent technical success rates, good
[see Tables 2 and 3]. Again, these results are very similar to those    clinical benefit, and low morbidity. In a study addressing 85
reported in the meta-analysis (range, 0% to 64%; mean response          renal artery stenoses in 66 FMD patients, hypertension was
rate, 38%).55 A significant percentage of treated patients (range,      cured or improved in 98% of patients after renal angioplasty,
0% to 48%; mean, 21%) also experienced post-PTAS worsening              and all patients with elevated creatinine levels exhibited
of renal function.                                                      improved or stabilized renal function.94 Another study, involv-
   Although all investigators agree that worsened post-PTAS renal       ing a series of older FMD patients (mean age, 59 years) with
function represents a treatment failure, it is less clear whether an    longstanding hypertension (mean duration, 13 years), report-
unchanged serum creatinine concentration should be considered           ed somewhat different blood pressure response results.95 At
beneficial to the patient. In one study, 88% of patients treated for    follow-up more than 3 years later, hypertension was cured in
renal dysfunction exhibited improved or stabilized serum creati-        14% of patients and alleviated in 74%. Both studies support-
nine levels after angioplasty, stenting, or both.92 Only 25% of         ed the general consensus that medial fibroplasia of the main
patients, however, showed sustained responses over a 5-year fol-        renal artery can be adequately treated by means of primary
low-up period; the remainder demonstrated continuing deteriora-         angioplasty, with stent placement reserved for technical fail-
tion of renal function.These results contrast sharply with those of     ures. Furthermore, it appeared that a beneficial clinical
reports addressing open surgical treatment of renal dysfunction,        response was seen after endovascular intervention and that
which documented durable improvement or stabilization rates of          this response was more pronounced in younger patients with
85% to 93% and 5-year dialysis-free survival rates of 50% to            a shorter duration of hypertension.
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6 VASCULAR SYSTEM                                                                                                                 23 RENOVASCULAR DISEASE — 12


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Acs0623 Endovascular Procedures For Renovascular Disease

  • 1. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 23 RENOVASCULAR DISEASE — 1 23 ENDOVASCULAR PROCEDURES FOR RENOVASCULAR DISEASE Juan Ayerdi, M.D.,Matthew S.Edwards, M.D., and Kimberley J.Hansen, M.D., F.A.C.S. The treatment of renovascular disease is currently in a state of evolu- Contrast-Related Considerations tion. Open surgical revascularization [see 6:22 Open Procedures for Patients with known renovascular disease typically have a high Renovascular Disease] remains the gold standard, having demonstrat- prevalence of associated medical comorbidities (e.g., diabetes ed its durability and efficacy in treating renovascular hypertension mellitus, congestive heart failure, chronic renal insufficiency, and and ischemic nephropathy; however, it is associated with substantial diuretic-induced intravascular volume depletion). These condi- morbidity and mortality, even when performed in centers with ex- tions may necessitate alterations in the usual routines for patient tensive experience.1-4 As a result, endovascular techniques for renal preparation and use of iodinated contrast agents. Such agents are revascularization, including percutaneous transluminal angioplasty known to be capable of impairing excretory renal function,20 with or without endoluminal stent placement (PTAS), have emerged sometimes permanently.The risk of this complication is highest in as another option for the revascularization of occlusive renal artery persons with preexisting dehydration,21 renal insufficiency,22-24 or lesions. Compared with conventional open surgical revasculariza- diabetes mellitus.25-27 Administration of higher volumes of iodi- tion, these endovascular techniques offer a number of potential ben- nated contrast material28,29 and use of high-osmolarity agents25-27 efits (e.g., decreased morbidity, lower mortality, shorter recovery may also increase the risk of postprocedural renal function impair- times, and reduced hospital resource utilization); however, they also ment. Several reports, however, have demonstrated that peripro- possess certain potential drawbacks (e.g., reduced effectiveness and cedural administration of acetylcysteine30,31 and sodium bicar- decreased durability). bonate hydration32 can lower the risk of renal function impair- Predictably, controversy persists regarding the appropriate ment after angiography. application of surgical and endovascular therapies to the treat- In accordance with the available evidence, our current policy is to ment of renovascular disease, with proponents of each modality prepare all patients for aortorenal arteriography with saline hydra- citing selected literature to support their position. In what follows, tion (limited in patients with significant heart failure) and periproce- we review key technical aspects of endovascular renal revascular- dural administration of acetylcysteine, along with limited use of sodi- ization and summarize the current data on technical results, clin- um bicarbonate in patients who have preexisting renal insufficiency. ical outcomes, and associated complications. There is reason to Furthermore, we routinely select low-osmolarity iodinated contrast believe that improvements in our ability to select patients most agents in these patients and pay special attention to limiting the vol- likely to benefit from treatment,5-10 as well as the emergence of umes infused. In patients with moderate to severe preexisting renal technical developments aimed at preventing procedure-related insufficiency, carbon dioxide33,34 or gadopentate dimeglumine35 may embolization11-13 and long-term restenosis,14 may be on the hori- also be employed as an intra-arterial contrast agent to reduce or zon. Such advances, if realized, may further narrow the gap eliminate the use of iodinated contrast material. Our practice with between the clinical results of surgical renal revascularization and such patients is to use carbon dioxide or gadopentate dimeglumine for initial localization [see Figure 1a] and selective cannulation [see those of its endovascular counterpart and may improve the mar- Figure 1b] of the renal artery, then to employ an iodinated contrast ginal benefit and safety of renal artery PTAS. agent in small volumes for definitive planning and performance of the required intervention. Preoperative Evaluation Technical Considerations The general principles of preoperative evaluation and patient Choice of arterial access route Femoral artery access, selection for persons being considered for renal revascularization, when feasible, is the most versatile and low-risk option. For non- whether open or endovascular, will not be described in detail in selective renal arteriography, either femoral artery provides ade- this chapter. As a rule, our group reserves renal artery PTAS for quate access. For selective renal cannulation, however, it is gener- patients in whom open surgical repair is considered high risk or ally better to use the femoral artery contralateral to the renal who refuse such repair. artery being addressed; this approach takes advantage of the ten- CONTRAST ARTERIOGRAPHY dency of the catheter to track preferentially toward the contralat- eral aortic wall and facilitates cannulation of the renal ostia. Despite advances in diagnostic imaging and functional testing If the patient has downsloping renal arteries or if femoral access that allow noninvasive identification of patients with renovascular is not advisable, brachial artery access is a useful alternative. It is disease,15-19 the formulation of an open surgical or endovascular preferable to access the left brachial artery so as not to cross the therapeutic plan continues to depend on visualization of the renal origin of the right common carotid artery. Access may be estab- artery anatomy by means of angiography. Accordingly, contrast lished by means of either percutaneous or open techniques. The arteriography of the renal arteries should be considered an inte- risk of complications is higher with percutaneous brachial artery gral component of the therapeutic armamentarium for clinically access, and the maximum permissible sheath and catheter sizes significant renal artery lesions. are smaller.36 Accordingly, we generally use an open approach for
  • 2. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 23 RENOVASCULAR DISEASE — 2 a b Figure 1 (a) Shown is bilateral high-grade renal artery stenosis visualized by using carbon dioxide angiogra- phy to localize the renal ostia. (b) Shown is selective right renal artery cannulation, with placement of a 6 French left internal mammary artery (LIMA) guide catheter and selective renal arteriography using hand- injected half-strength iso-osmolar contrast material. brachial artery access, with puncture, cannulation, and closure eter have been gently advanced into the renal artery ostia, contrast carried out under direct vision. material is injected by hand to confirm intraluminal placement. Selective images are then obtained with low-volume power injection Choice of imaging views Aortography and selective renal or hand injection (our preference) of contrast material [see Figure 4]. arteriography with multiple projections are necessary for full radi- The proximal third of the left renal artery usually courses anterior- ographic evaluation of the renal arteries and the juxtarenal aorta. ly, the middle third transversely, and the distal third posteriorly; the Initial anteroposterior (AP) images of the visceral aorta are ob- tained by delivering power contrast injections through a flush catheter with multiple side holes positioned just beneath the diaphragm at the level of the first lumbar vertebra.These initial AP views provide an overview of the renal artery and the perivisceral aortic anatomy [see Figure 2]. All further nonselective images of the renal arteries should be obtained by moving the catheter to a loca- tion below the origin of the superior mesenteric artery to prevent contrast opacification of the visceral vessels, which could obscure the anatomic details of the renal arteries. The renal arteries usually arise from the anterolateral or the posterolateral aspect of the aorta. As a result, lesions within the renal ostia often are not seen or appear insignificant on AP aor- tograms. Oblique aortography or oblique selective renal arteriog- raphy projects these portions of the vessel in profile and thus are often better at identifying any renal ostial lesions present. As a rule, the most useful projection for visualizing the renal ostia is a 15º to 30º left anterior oblique view, though other oblique views may also be necessary.37,38 Previously obtained axial images of the renal ori- gins (i.e., computed tomographic scans) may allow better estima- tion of the necessary degree of obliquity and permit the use of smaller amounts of iodinated contrast material and lower doses of ionizing radiation [see Figure 3]. For full delineation of lesions within the body of the renal artery, selective arteriographic views may be required. Selective cannula- tion is usually performed with an angled catheter (e.g., a cobra cath- eter, a Sos catheter, or a renal double-curve catheter) in combina- tion with a steerable guide wire; the varying configurations of the available catheters offer specific advantages in particular anatomic Figure 2 Anteroposterior (AP) aortogram is obtained by delivering situations. Before selective renal artery cannulation, we typically a power injection of iso-osmolar iodinated contrast material through administer heparin intravenously. Once the guide wire and the cath- a 5 French pigtail catheter positioned at the L1-2 interspace.
  • 3. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 23 RENOVASCULAR DISEASE — 3 Arteriographic Findings As noted (see above), the primary role for contrast arteriogra- phy in the treatment of renovascular disease is concerned with therapy rather than diagnosis. Angiography is most frequently per- formed to assess a renal artery lesion previously identified by means of renal duplex ultrasonography, CT arteriography, or magnetic resonance arteriography either before or as part of a therapeutic intervention. Most clinically significant renal artery lesions are caused by atherosclerotic disease or fibromuscular dys- plasia (FMD), with a small minority occurring secondary to other pathologic states. Each of these two major pathologic entities is associated with specific imaging characteristics and specific treat- ment considerations. Atherosclerotic renovascular disease Atherosclerosis of the renal artery accounts for roughly two thirds of all renovascular lesions. Elderly persons with multiple comorbid medical condi- tions and manifestations of atherosclerosis are most frequently Figure 3 Axial CT scan image of the renal artery origins allows affected.41-44 Atherosclerotic renal lesions generally represent a estimation of the degree of obliquity required for optimal imaging continuation of a process that begins in the aorta and spills over of the renal ostia. into the origin of the renal vessels [see Figure 5]. These lesions are characterized by an eccentric, irregular narrowing of the ostium and the proximal portion of the renal artery [see Figure 6]. In the majority of cases, the lesions are limited to the ostia and the prox- imal renal artery, and the two sides are affected equally.45 The aor- tic origin of the lesion has important implications for treatment. Placement of an endovascular stent into the proximal renal artery, without the aortic origin of the plaque being taken into account, may result in residual or recurrent disease. Occlusions of the renal artery are also common in patients with clinically significant lesions [see Figure 7] and frequently occur in the setting of con- tralateral renal artery stenosis.2,3 Fibromuscular dysplasia FMD is a term used to describe a group of histologically distinct pathologic conditions of the arte- rial wall that most commonly affect the main renal artery and its branches. FMD of the renal artery, with resultant renal artery stenosis, is responsible for approximately 25% to 30% of treated cases of renovascular hypertension.45 The lesions are usually cate- gorized according to the layer of the arterial wall predominantly Figure 4 Shown is selective arteriography of the right renal artery using hand-injected iso-osmolar contrast material through a complexly curved Simmons catheter. right renal artery generally pursues a more consistent posterior course. For full delineation of lesions in the various segments, oblique and cranial-caudad rotated images may be necessary. Adjunctive measures The performance of arteriographic imaging of the renal arteries also affords the surgeon the opportu- nity to employ other measures to characterize a renal artery lesion. For example, the hemodynamic effects of angiographically detect- ed stenosis or the treatment thereof can be assessed by making direct pressure measurements proximal and distal to the lesion. In general, we consider any pressure gradient greater than 10 mm Hg to be indicative of hemodynamically significant renovascular dis- ease. Additional anatomic information can be obtained by means of intravascular ultrasonography of the renal artery, which can provide detailed information on plaque morphology, vessel size, and potential dissection flaps to complement the data obtained Figure 5 Aortic endarterectomy specimen demonstrates the through arteriography.39,40 pathologic basis of atherosclerotic renovascular disease.
  • 4. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 23 RENOVASCULAR DISEASE — 4 beads [see Figure 8], an appearance created by weblike stenotic areas with intervening areas of poststenotic dilatation. These lesions are frequently unilateral, and they can also produce a renal artery aneurysm or dissection.47 Stenotic medial fibroplasia of the main renal artery is among the lesions most amenable to endovas- cular treatment. In our view, however, the presence of branch ves- sel disease or aneurysms precludes such treatment. Perimedial dysplasia accounts for approximately 15% of cases of FMD and is most commonly manifested by the appearance of multiple irregular stenoses without microaneurysms.46 Intimal fibroplasia is the least common variant of FMD, representing fewer than 5% of recognized cases, and the typical lesions are smooth concentric stenoses.45,46 In general, perimedial dysplasia and intimal fibroplasia tend to respond less well to endovascular treatment than medial fibroplasia does. Operative Planning PATIENT PREPARATION Patient preparation for renal artery PTAS is similar to that rou- tinely carried out for diagnostic arteriography. Oral intake of food and liquid is stopped at midnight the evening before the procedure. Figure 6 Magnified preintervention aortogram demonstrates Warfarin is discontinued at least 4 days beforehand; aspirin and ostial right renal artery atherosclerotic stenosis. clopidogrel are continued. Intravenous fluids and acetylcysteine are administered the evening before the procedure, with care taken to involved—hence the terms medial fibroplasia, perimedial dyspla- avoid fluid overload in patients with impaired cardiac function. Rou- sia, and intimal fibroplasia. Medial fibroplasia is the most com- tine medications, with the exception of angiotensin-converting en- mon variant, representing 85% of recognized cases. It is encoun- zyme inhibitors and angiotensin receptor antagonists, are taken on tered almost exclusively in women, most commonly in the third or the morning of the procedure with a sip of water. A first-generation fourth decade of life.45,46 The arteriographic pattern most fre- cephalosporin is administered intravenously 30 minutes before the quently associated with medial fibroplasia resembles a string of procedure unless the patient is allergic. After the intervention, the patient is observed in the hospital overnight to check for access-site problems and severe alterations in blood pressure. Acetylcysteine is continued throughout the hos- pital stay, and oral administration of clopidogrel is initiated the evening after the procedure. The patient continues to take clopi- dogrel for at least 30 days after revascularization and remains on aspirin therapy indefinitely. CORRELATION OF DIAGNOSTIC IMAGES WITH CLINICAL FINDINGS Once the diagnostic portion of the procedure is completed, the images obtained are closely examined and correlated with the patient’s clinical presentation. Intra-arterial pressure measure- ments are occasionally misleading in renal vessels. Because most renal arteries are approximately 5 to 6 mm in diameter, a stenotic lesion that causes a greater than 60% reduction in the luminal diameter leaves only 2.0 to 2.5 mm of patent lumen. A 4 or 5 French diagnostic catheter may completely occlude this narrowed lumen, thus resulting in an inaccurately low pressure measure- ment distal to the stenosis. Accordingly, it is our practice to assess the anatomic arteriographic information in the light of the func- tional significance of the lesion as determined by either renal vein renin assays or duplex ultrasonography. MATERIALS AND INSTRUMENTS The materials commonly used for renal artery PTAS at our center include various guide wires, catheters, sheaths, balloons, and stents [see Table 1]. The basic principles underlying the use of Figure 7 Aortogram demonstrates right renal artery stenosis and these devices are outlined more fully elsewhere [see 6:8 Fun- left renal artery occlusion with distal renal artery reconstitution. damentals of Endovascular Surgery].
  • 5. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 23 RENOVASCULAR DISEASE — 5 ter and the introducer sheath are exchanged over a 0.035 in. guide wire so that an access platform can be established that will provide secure renal artery access for the therapeutic intervention. Most angioplasty and stenting devices in current use will pass through a 6 French lumen. Access options include guide sheaths and guide catheters. Common to both of these options is the pro- vision of a long mechanical support segment for guide-wire place- ment that affords direct access to the renal artery for easy passage of therapeutic devices to the target lesion [see Figure 9]. Such sys- tems vary in shape and diameter and come in multiple configura- tions to facilitate renal artery access in different situations. After the tip of the guide catheter is positioned at or within the renal artery orifice, guide-wire access across the lesion is obtained. For all subsequent manipulations, the sheath or the guide catheter should not be advanced beyond the orifice, because the nonta- pered tip may injure the vessel. Depending on the type, severity, and location of the lesion, a 0.35, 0.18, or 0.14 in. guide wire with a floppy radiopaque tip is chosen.The smaller guide-wire systems appear to have inherent advantages, in terms of ability to cross Figure 8 Selective right renal arteriogram demonstrates findings tighter stenoses, limitation of renal artery trauma, and liberation of indicative of medial fibroplasia. emboli, but whether these apparent advantages are real remains to be proved. Once the guide wire is in place, the access platform is secured and remains in place until the intervention and any Operative Technique postintervention imaging are complete. STEP 1: SECURING OF ACCESS TO RENAL ARTERY FOR STEP 2: TRANSLUMINAL ANGIOPLASTY THERAPEUTIC INTERVENTION With the guide wire secured distal to the lesion, therapeutic Once the decision for endovascular intervention is made, the pa- intervention may proceed. Both coaxial systems (in which the tient is systemically heparinized, and the 5 French diagnostic cathe- entire catheter is exchanged over the wire, so that an assistant is Table 1 Standard Equipment for Renal PTAS Device Category Type Proprietary Name Length Diameter Initial Starter 3 mm J 180 cm 0.035 in. Magic Torque 180 cm 0.035 in. Guide wires Selective Platinum Plus, V-18 145–180 cm 0.018 in. Transend, GuardWire 165–200 cm 0.014 in. Flush angiography Pigtail 70 cm 5 Fr Cobra C1 or C2 65 cm 5 Fr Selective: diagnostic Contra 2 65 cm 5 Fr VS–1 or Sos 65 cm 5 Fr Simmons 65 cm 5 Fr Catheters Renal Double Curve 55 cm 6 Fr LIMA 55 cm 6 Fr Selective: guide JR 4 55 cm 6 Fr Hockey Stick 55 cm 6 Fr Pressure-measuring Straight Glide 90 cm 4 Fr Initial access 10 cm 5 Fr Sheaths Therapeutic access 10 cm 6 Fr Pinnacle Destination 45 cm 6 Fr Selective: guide Flexor Check Flow ANL2 45 cm 6 Fr 1.5–2.0 cm balloon 3 mm balloon Predilation Savoy, Gazelle, Aviator, Symmetry 75–90 cm shaft 5 Fr sheath Angioplasty balloons 1.5–2.0 cm balloon 4–7 mm balloon Therapeutic Savoy, Gazelle, Aviator, Symmetry 75–90 cm shaft 5 Fr sheath 12–29 mm stent 5–7 mm stent Stents* Balloon-expandable Genesis, Express, Racer 75–90 cm shaft 6 Fr sheath *None of these stents are FDA-approved for use in renal arteries.
  • 6. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 23 RENOVASCULAR DISEASE — 6 a b Figure 9 Shown are (a) a guide catheter inserted through a short 6 French arteri- al sheath and (b) a diagnostic catheter inserted through a guide sheath. required to control the wire during intervention and catheter STEP 3: ENDOLUMINAL STENTING exchange) and monorail or rapid-exchange systems (in which only Endovascular stent placement may be performed either as a pri- the distal portion of the catheter is over the wire, so that a single mary procedure or as a secondary procedure in response to sub- operator can control the wire during intervention and catheter optimal results from angioplasty. Most FMD lesions and nonos- exchange) are available for renal artery intervention. tial atherosclerotic lesions respond well to angioplasty alone. Regardless of the system chosen, the principles of intervention Secondary stent placement should, however, be considered for remain the same. Transluminal angioplasty of the renal artery nonostial lesions that do not respond appropriately to angioplasty. may be performed either as the sole therapy for a renal artery Secondary stent placement is typically performed to address elas- lesion or as a means of predilating a lesion so that an endolumi- tic recoil, residual stenosis (> 30%), pressure gradients (> 10 mm nal stent can be placed. Angioplasty may also be employed to Hg), and myointimal flaps or dissections. Either balloon-expand- treat recurrent renal artery stenoses after surgical or endovascu- able or, less commonly, self-expanding stents may be employed in lar therapy. Angioplasty is an effective stand-alone therapy in the renal artery. Typically, balloon-expandable stents have greater most cases of main renal artery disease (FMD and nonostial ath- radial strength and can be placed more precisely, whereas self- erosclerosis) but is frequently ineffective for atherosclerotic ostial expanding stents are more flexible and conform more readily to and proximal renal artery disease. the shape of the lumen.We employ balloon-expandable stents pri- The angioplasty balloon size is chosen on the basis of quantita- marily in the treatment of ostial atherosclerotic lesions, where their tive angiographic images. Direct cut-film images with ball-bearing advantages are particularly useful. or marker-catheter reference points may be used, as may the quan- In general, the technical aspects of stent placement parallel titative software packages available on most contemporary digital those of transluminal angioplasty. Frequent hand injections of angiographic systems. In general, the angioplasty balloon should small amounts of contrast material through the guide sheath or be slightly larger than the adjacent normal artery for primary catheter are employed to guide the stent into position across the treatment and somewhat smaller for predilation of a stenotic lesion before deployment [see Figure 10]. After the stent has been lesion. For predilation before endoluminal stent placement, we deployed, a completion angiogram is performed while guide-wire usually employ a 3 × 20 mm low-profile angioplasty balloon.This access to the renal artery is maintained. This is accomplished by choice tends to make stent passage less traumatic and helps in esti- hand injection of contrast through the guide sheath or catheter. mating the stent diameter and length required. For the treatment of ostial or proximal renal artery lesions, it is During inflation of the angioplasty balloon, the aortic origin of preferable to position the stent with 1 to 2 mm extension into the most ostial plaques is indicated by the appearance of a visible aorta. Frequent hand injection of contrast material through the “waist,” and the image can be centered over a bony landmark to guide sheath allows precise placement of the stent and helps pre- facilitate subsequent stent placement. It is not unusual for the vent misdeployment. If the stent is placed too far into the artery, patient to experience some discomfort during balloon inflation. the true renal orifice is not supported, and there is a greater This discomfort should resolve quickly when the balloon is deflat- chance of residual or recurrent disease.48-52 Such recurrent disease ed; if it does not, renal artery trauma should be suspected. It is our often does not respond to further endovascular attempts; accord- practice to inflate the balloon slowly to its fully inflated profile at the ingly, it is advisable to use the shortest possible stent that will ade- rated nominal pressure, then maintain inflation for 30 to 45 sec- quately support the lesion. In addition, a stent that extends well onds before deflation. out into the distal renal artery can make later surgical options Once the balloon has been completely deflated, it is removed, more difficult53 and typically carries a higher failure rate. and selective angiography is repeated to assess the response of the A balloon-expandable stent is deployed by inflating the angio- lesion to angioplasty and check for complications. Guide-wire plasty balloon on which it is mounted. In the past, these stents had access must be maintained until the end of the procedure so that to be crimped and hand-mounted on the angioplasty balloon, complications or unsatisfactory results (e.g., dissection or residual which made their delivery somewhat insecure. Currently available stenosis) can be addressed. stents, however, come securely premounted on low-profile deliv-
  • 7. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 23 RENOVASCULAR DISEASE — 7 ery systems capable of passing across most lesions with minimal Postoperative Care or no predilation. We deploy these stents with 1 to 2 mm exten- Longitudinal follow-up of all patients undergoing renal revas- sion into the aorta, guided by anatomic information provided by cularization is mandatory to check for recurrent disease, con- previous positioning over bony landmarks. Self-expanding stents, tralateral disease, and deterioration of clinical benefit, as well as though not commonly applied to the treatment of renovascular other preventable cardiovascular and peripheral vascular condi- disease, can also be employed in this setting. These devices are tions. Our current approach to follow-up entails clinical visits at 1, deployed by retracting an outer membrane of the delivery device 3, 6, 9, 12, 18, and 24 months after renal artery PTAS, with renal to expose the stent. Care must be taken during deployment to duplex ultrasonography, blood pressure measurement, and serum ensure that foreshortening of the stent does not compromise cov- erage of the lesion. creatinine measurement at each visit. After 24 months, this inten- After a stent is deployed, there may be residual narrow areas sive early follow-up is relaxed to a yearly visit schedule if no con- within the stent that necessitate balloon dilatation. These areas ditions necessitating shorter visit intervals have been identified. may be visible on fluoroscopic evaluation of the stent, or they may Recurrent disease after renal stenting is a significant concern, and be detected during postdeployment selective renal angiography. disease that recurs within the stent itself can be a particularly chal- After all therapeutic measures have been completed, the tech- lenging problem [see Figure 11a]. Because most such recurrences are nical result is assessed and undetected defects sought by means of related to intimal hyperplasia, repeat balloon angioplasty generally repeat pressure-gradient measurements, intravascular ultrasonog- does little to improve the situation. Initial dilatation with a Cutting raphy, or both. When a satisfactory result is obtained, the guide Balloon (Boston Scientific, Natick, Massachusetts) is extremely use- wire and the sheath are removed and hemostasis is secured. ful for releasing the fibrous scar tissue of the restenotic lesion and al- Although it is possible to perform bilateral renal interventions in a lowing subsequent dilatation to a larger diameter with a convention- single procedure, we prefer, when possible, to stage these inter- al angioplasty balloon.The Cutting Balloon consists of a noncompliant ventions so as to minimize contrast loads. balloon with three or four atherotomes (microsurgical blades) mount- a b c Figure 10 (a) The orifice of a right renal artery with high-grade ostial stenosis is catheterized with a 6 French cobra catheter, and the lesion is crossed with a 0.014 in. guide wire. (b) A balloon- mounted stent is positioned across the renal artery stenosis with the help of intermittent con- trast injections and bony landmarks. (c) A fully expanded stent is positioned in the renal artery.
  • 8. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 23 RENOVASCULAR DISEASE — 8 a b c Figure 11 (a) Shown is high-grade recurrent in- stent restenosis of the right renal artery. (b) The Cutting Balloon is useful in dealing with such lesions. (c) Dilation with a 4 × 15 mm Cutting Balloon is followed by dilation with a standard 6 × 20 mm angioplasty balloon, and a completion angiogram is obtained. ed longitudinally on its outer surface [see Figure 11b].When the device fusion, surgical intervention, and deep vein thrombosis.There was is inflated, the atherotomes score the intimal hyperplasia within the no apparent association between pretreatment patient characteris- stent; the balloon is then rotated and reinflated to score the lesion in tics and the subsequent incidence of major complications. Two multiple planes.To date, this technique has been used primarily in patients (1.1%) died within 30 days after the procedure. coronary arteries, but it has also been applied to the treatment of renal artery in-stent restenosis.54 After the lesion has been scored, a larger Outcome Evaluation balloon is inserted and inflated to redilate the lesion [see Figure 11c]. To be considered successful, renal artery revascularization should (1) improve quality of life, (2) reduce the incidence of Complications adverse cardiovascular disease events, (3) slow or halt the pro- gression of chronic renal insufficiency, (4) lower the incidence Complications can arise at any point during renal artery PTAS or of dialysis-dependent renal failure, and (5) improve overall sur- during the early postoperative period. Potential complications in- vival. Unfortunately, few studies addressing these clinical out- clude access-site complications (e.g., hematoma, pseudoaneurysm, come measures have been performed or reported. Thus, the retroperitoneal hemorrhage, arteriovenous fistula, and closure-device outcome of renal revascularization is currently assessed on the infection), contrast-mediated allergic reactions or nephrotoxicity, basis of (1) the extent to which the procedure is anatomically or atheroembolism, and direct renovascular trauma. In a meta-analysis technically successful and (2) the degree to which the proce- published in 2000, the reported complication rate after renal PTAS dure alleviates or cures associated hypertension and ischemic ranged from 0% to 40% (mean rate, 11%).55 The most frequently nephropathy. Technical success and the response of hyperten- reported complications were hematomas at arterial access sites. sion or renal dysfunction to therapy are assumed to be the Severe complications occurred in 9% of patients and included renal mechanisms by which the five important clinical outcomes list- failure, segmental renal infarction, perinephric hematoma, and renal ed are achieved. artery thrombosis.The mean mortality was 1%. Interpretation of the results of renal artery PTAS as reported in A large single-center retrospective review of complications after the current literature is challenging. Despite the publication of endovascular treatment with renal artery stenting reported similar hundreds of reports on this procedure, it remains unclear how results.56 Major complications occurred after 15 of 179 procedures renal artery PTAS compares with surgical renal revascularization (8.4%) and included renal infarction, permanently increased and whether renal artery PTAS conveys any meaningful benefit to serum creatinine concentration, dialysis dependence, blood trans- patients beyond what can be achieved with medical therapy alone.
  • 9. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 23 RENOVASCULAR DISEASE — 9 Table 2—Results after Primary Percutaneous Transluminal Angioplasty for Atherosclerotic Renal Artery Stenosis Patients with Renal Function Response (%) Hypertension Response (%) Major Patients Technical Renal Restenosis Complication Study (N) Success Dysfunction Rate (%) Improved Unchanged Worsened Cured Improved Failed Rate (%) Rate (%) (N) Canzanello (1989)60 100 73 66 52 48 59 41 19 20 Klinge (1989)62 134 78 NR NR 11 78 10 16 11 Baert (1990)58 165 83 NR NR 32 36 32 10 11 Weibull (1993)67 29 83 NR 21 75 4 13 71 17 25 17 Losinno (1994)64 153 95 59 27 67 6 12 51 37 NR 8 Bonelli (1995)59 190 82 NR No change in mean SCr 8 62 30 10 23 Hoffman (1998)61 50 58 36 44 23 33 3 64 32 27 14 Klow (1998)63 295 92 NR No change in mean SCr 5 59 31 40 8 Zuccala* (1998)68 99 92 33 39 50 11 18 44 48 17 8 Paulsen (1999)69 135 90 79 23 56 21 6 41 53 45 9 Van de Ven (1999)65 41 57 22 18 55 27 5 44 51 48 29 Baumgartner (2000)70 163 95 107 33 42 25 43 57 35 3 Van Jaarsveld (2000)66 56 91 NR No change in mean SCr 7 61 32 48 5 Total 1,610 86 402 32 51 17 11 54 35 25 12 *All diabetic patients. NR—not reported SCr—serum creatinine concentration These shortcomings in our understanding of renal artery PTAS HYPERTENSION RESPONSE (and of surgical renal revascularization, for that matter) stem Three randomized, controlled studies have compared endovas- largely from the lack of well-designed clinical trials investigating cular surgery with medical treatment of renovascular hyperten- these questions. Such trials will ultimately be necessary to estab- sion. These studies provide the best available data on the efficacy lish the utility and safety of renal artery PTAS in the treatment of of endovascular therapy for managing hypertension, but they are renovascular disease. Until such trials are performed, interpreta- limited in that they all investigated the use of renal artery angio- tion of the existing literature is the only available guide to the pru- plasty without primary stent placement. The first study involved dent application of renal artery PTAS. 49 patients with unilateral renal artery stenosis who were ran- TECHNICAL SUCCESS domly assigned to either angioplasty or best medical hypertension treatment.90 The angioplasty group demonstrated no statistically Technical success is defined on the basis of angiographic find- significant decrease in blood pressure; however, it did demonstrate ings at the completion of renal artery PTAS. Criteria include com- improvement in hypertension control, as evidenced by a signifi- plete stent coverage of the targeted lesion (if a stent was used) and cant reduction in the amount of antihypertensive medications residual diameter-reducing stenosis of less than 30%.57 Angio- plasty as stand-alone treatment of renovascular disease is of limit- required. The second study, reported by the Scottish and ed applicability, especially in cases of atherosclerotic disease of the Newcastle Renal Artery Stenosis Collaborative Group, involved renal ostia (the most commonly encountered lesion). The reason 55 patients who were randomly assigned to either angioplasty or is that ostial renovascular disease usually represents the extension best medical antihypertensive therapy.91 Patients with both unilat- of aortic-based plaque, which possesses substantial inherent recoil eral and bilateral renal artery stenosis were included in this study. and thus is resistant to dilatation unless mechanical support is There was a modest improvement in blood pressure control in the added to help maintain the enlarged lumen. angioplasty group, but this benefit was confined to those patients A review of the literature on renal artery angioplasty for ath- who had bilateral disease. None of the patients were cured of their erosclerotic renovascular disease determined that immediate tech- hypertension. The third study—the largest prospective, random- nical success was reported in 86% of cases [see Table 2].58-70 The ized trial reported to date in this area—was performed by the immediate technical success rate was higher when a stent was Dutch Renal Artery Stenosis Intervention Cooperative Study employed, especially in cases of ostial disease. A review of the lit- Group.66 A total of 106 patients were randomly assigned to either erature on primary stenting for atherosclerotic renovascular dis- renal artery angioplasty or best medical therapy for renovascular ease determined that primary use of stents yielded an immediate hypertension. At 12 months, there was no significant reduction in technical success rate of 98% [see Table 3].5,48,50,51,65,70-89 The supe- either systolic or diastolic blood pressure, though multiple treat- riority of primary stenting for ostial lesions was confirmed in a ment crossovers occurred that might have skewed the results prospective clinical trial.65 toward the best medical therapy arm.The authors concluded that
  • 10. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 23 RENOVASCULAR DISEASE — 10 Table 3—Results after Primary Arterial Stent Placement for Atherosclerotic Renal Artery Stenosis Patients with Renal Function Response (%) Hypertension Response (%) Major Study Patients Technical Renal Restenosis Complication Success Dysfunction Rate (%) Rate (%) (N) Improved Unchanged Worsened Cured Improved Failed Rate (%) (N) Rees (1991)84 28 96 14 36 36 29 11 5 36 39 18 Kuhn (1991)81 8 92 NR NR 22 34 44 17 13 Joffre (1992)80 11 91 4 50 50 0 27 64 9 18 13 Hennequin (1994)77 15 100 6 20 40 40 7 93 0 27 19 Macleod (1995)83 28 100 16 25 75 0 40 60 17 19 Van de Ven (1995)88 24 100 NR 33 58 8 0 73 27 13 13 Dorros (1995)72 76 100 29 28 28 45 6 46 48 25 11 Henry (1996)51 55 100 10 20 80 18 57 24 9 3 Iannone (1996)79 63 99 29 36 46 18 4 35 61 14 32 Harden (1997)76 32 100 32 35 35 29 NR 13 19 Blum (1997)48 68 100 20 0 100 0 16 62 22 17 0 Boisclair (1997)50 33 100 17 41 35 24 6 61 33 0 21 Rundback (1998)86 45 94 45 18 53 30 NR 26 9 Fiala (1998)5 21 95 9 0 100 0 53 47 65 19 Dorros (1998)73 163 99 63 No change in mean SCr 1 42 57 NR 14 Tuttle (1998)87 120 98 74 16 75 9 2 46 52 14 4 Gross (1998)75 30 100 12 55 27 18 0 69 31 13 NR Henry (1999)78 200 99 48 29 67 2 19 61 20 11 2 Rodriguez-Lopez (1999)85 108 98 32 No change in mean SCr 13 55 32 26 12 Van de Ven (1999)65 40 88 29 17 55 28 15 43 42 14 30 Baumgartner (2000)70 64 95 NR 33 42 25 43 57 28 9 Giroux (2000)74 30 95 21 76 24 53 47 NR NR Lederman (2001)82 300 100 111 8 78 14 70 30 21 2 Bush (2001)71 73 89 50 23 51 26 NR NR 9 Zeller (2004)89 456 98 239 34 39 27 46 54 NR NR Total 2,091 98 910 22 56 22 10 51 39 19 9 NR—not reported SCr—serum creatinine concentration angioplasty had little advantage over antihypertensive therapy in To date, only one prospective, randomized, controlled study has the treatment of renovascular hypertension. compared endovascular treatment with surgical revascularization for A 2000 meta-analysis examined data from retrospective reports the treatment of renovascular hypertension.67 In this report, 58 describing a total of 1,322 patients who were treated with renal patients with renovascular hypertension were randomly assigned to artery angioplasty or stenting.55 The overall hypertension cure rate either surgical revascularization or angioplasty. In both groups, hyper- was 20%, and 49% of the patients had improved blood pressure tension was cured or improved in approximately 90% of patients. control. In a similar review of data from 36 reports on primary However, more than half of the patients in whom angioplasty failed renal angioplasty or stent placement for the treatment of athero- were switched to the surgical arm for revascularization. On the basis sclerotic renal artery stenosis [see Tables 2 and 3], the reported of these results, the authors recommended angioplasty as the treat- treatment indications included hypertension, renal insufficiency, ment of choice for selected renovascular lesions contributing to reno- and a combination of the two.The percentage of patients cured of vascular hypertension, with aggressive follow-up and repeat interven- hypertension ranged from 0% to 32% (mean, 10%), and the per- tion (endovascular and surgical) carried out as needed. centage of patients experiencing improved blood pressure control Another group of investigators, however, reported that the ben- ranged from 5% to 93% (mean, 53%). eficial blood pressure response seen after open surgical repair for
  • 11. © 2005 WebMD, Inc. All rights reserved. ACS Surgery: Principles and Practice 6 VASCULAR SYSTEM 23 RENOVASCULAR DISEASE — 11 failed angioplasty may be less than that seen in patients who 55%.2-4 Furthermore, patients with ischemic nephropathy whose undergo primary surgical repair without previous endovascular renal function did not change after surgical revascularization had treatment.53 Moreover, a previous endovascular procedure may increased rates of death and dialysis dependence during follow-up make open surgical repair technically more demanding, especially that were similar to those noted in patients with poorer renal func- if an endoluminal stent is present. tion after revascularization.2,3 These findings raise serious ques- At present, there are no level I data demonstrating any associ- tions about the concept of stabilized renal function and suggest ation between improved hypertension control after renal artery that improved postprocedural renal function may be the most per- PTAS and either increased survival or reduced morbidity and tinent surrogate outcome marker for predicting improved survival mortality from adverse cardiovascular events. In fact, very few and dialysis independence. reports contain any data on these important clinical outcomes, LONG-TERM COMPLICATIONS and those that do have not documented any significant differ- ences between medical management and renal artery Complications and suboptimal outcomes may also develop in a PTAS.66,90,91 There is some evidence in the surgical literature of delayed manner. The principal long-term complications include associations between hypertension response and a decrease in restenosis of the renal artery and inadequate durability of clinical adverse cardiovascular events; notably, however, these associa- benefit. Restenosis is a common occurrence with all catheter-based tions appear to exist only for persons whose renovascular hyper- methods of revascularization. According to the meta-analysis cited tension is cured.2 earlier,55 restenosis complicates 11% to 42% (mean, 26%) of renal artery angioplasties and 12% to 23% (mean, 17%) of renal artery RENAL FUNCTION RESPONSE stent procedures. Other studies have yielded very similar results [see Several factors hinder accurate assessment of the effect of renal Tables 2 and 3]. Restenosis may or may not be clinically significant. artery PTAS on renal function.To date, no prospective, controlled Accordingly, the decision whether to treat restenotic lesions should studies have compared renal function responses after medical, be made on the basis of the specific physiologic or clinical findings, surgical, and endovascular treatment of renal artery stenosis. not simply because restenosis is present. Most observational series report results from a diverse group of The beneficial clinical responses noted after renal artery PTAS patients whose baseline renal function and subsequent responses frequently are not durable. In two studies that reported on a to- to treatment vary widely. Interpretation of the existing renal func- tal of 222 individuals undergoing renal artery PTAS, the investiga- tion response data is further complicated by the insensitivity of se- tors found that the clinical response, especially the renal func- rum creatinine measurement (the most commonly employed in- tion response, was transient.92,93 Overall, at 5 years, 50% to 70% dicator of renal function in these studies) to changes in renal of patients exhibiting a positive hypertension response and function, especially in patients with serum creatinine levels lower fewer than 50% of those exhibiting a positive renal function than 1.2 mg/dl. response (defined as improvement or stabilization) retained any These limitations notwithstanding, a number of reports pub- benefit. This deterioration of clinical benefit occurred even lished between 1989 and 2004 provided useful data on renal func- though a patent renal artery was maintained in all cases. Such tion response after renal artery PTAS, expressed in terms of results stand in stark contrast to the documented durability of the change (or lack of change) in serum creatinine concentration [see clinical response after surgical revascularization and underscore the Tables 2 and 3]. With improvement defined as a 20% or greater need for close lifelong follow-up of all patients undergoing renal decrease in serum creatinine concentration, response rates ranging revascularization.1-4 from 0% to 55% were observed (mean, 22%). These results are OUTCOMES AFTER RENAL ARTERY PTAS FOR FMD very similar to those reported in the 2000 meta-analysis cited ear- lier (range, 0% to 50%; mean response rate, 30%).55 A number of Patients with FMD respond to renal artery PTAS much dif- authorities also make use of the concept of “stabilized” renal func- ferently from those with renal artery atherosclerosis. FMD is tion, defined as a less than 20% change in serum creatinine con- most commonly manifested as medial fibroplasia in a young centration. By this definition, renal function was stabilized in the woman. In general, balloon angioplasty appears to be an majority of patients included in the studies published between acceptable treatment for adult patients with such lesions, and 1989 and 2004 (range, 23% to 100%; mean response rate, 53%) this approach yields excellent technical success rates, good [see Tables 2 and 3]. Again, these results are very similar to those clinical benefit, and low morbidity. In a study addressing 85 reported in the meta-analysis (range, 0% to 64%; mean response renal artery stenoses in 66 FMD patients, hypertension was rate, 38%).55 A significant percentage of treated patients (range, cured or improved in 98% of patients after renal angioplasty, 0% to 48%; mean, 21%) also experienced post-PTAS worsening and all patients with elevated creatinine levels exhibited of renal function. improved or stabilized renal function.94 Another study, involv- Although all investigators agree that worsened post-PTAS renal ing a series of older FMD patients (mean age, 59 years) with function represents a treatment failure, it is less clear whether an longstanding hypertension (mean duration, 13 years), report- unchanged serum creatinine concentration should be considered ed somewhat different blood pressure response results.95 At beneficial to the patient. In one study, 88% of patients treated for follow-up more than 3 years later, hypertension was cured in renal dysfunction exhibited improved or stabilized serum creati- 14% of patients and alleviated in 74%. Both studies support- nine levels after angioplasty, stenting, or both.92 Only 25% of ed the general consensus that medial fibroplasia of the main patients, however, showed sustained responses over a 5-year fol- renal artery can be adequately treated by means of primary low-up period; the remainder demonstrated continuing deteriora- angioplasty, with stent placement reserved for technical fail- tion of renal function.These results contrast sharply with those of ures. Furthermore, it appeared that a beneficial clinical reports addressing open surgical treatment of renal dysfunction, response was seen after endovascular intervention and that which documented durable improvement or stabilization rates of this response was more pronounced in younger patients with 85% to 93% and 5-year dialysis-free survival rates of 50% to a shorter duration of hypertension.
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