Anatomy, physiology, clinical features and Management of Patent Ductus Arteriosus on the Newborn (PDA)

1. Patent Ductus Arteriosus
of the Newborn
Sid Kaithakkoden MD
alavisaid@aol.com

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Anatomy and Physiology

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 Incidence
 PDA is a problem in ventilated very low
birth weight infants
 About 40% of these will have a large PDA
at 3 days of age

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 Diagnosis
– Early:
 Mostly silent, with no murmur
 BP may be low (systolic, diastolic and mean) with
normal pulse pressure
– Late:
 Murmur. Hyperactive precordium
 Increased pulses, Wide pulse pressure (These
are not reliable signs in the first few days)
 Congestive Heart Failure
 Cardiomegaly, Hepatomegaly
 Pulmonary congestion/oedema/plethora
 Clinical respiratory deterioration
 Rising PaCO2

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Investigations
 Echo:
 Rules out (most) congenital heart disease. Important to rule out
duct dependent lesions
 Establishes duct patency and size
 Indicates size of shunt. (ductus shunt best assessed by its
physical size, then by descending aortic flow pattern, then by
LA and LV size)
 Assesses atrial shunt and size
 C X-ray
 To look at heart size and lung fields
 ECG:
 Usually normal
 Do if ‘atypical’, PDA persists or suspicion on congenital heart
disease

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Management
 <1000gms and on IPPV or CPAP
– Echocardiogram
– Significant PDA: indomethacin
 Other babies on IPPV
– Investigate if clinical suspicion
 Indomethacin
 Fluid restriction
– There is no evidence that fluid restriction per se results
in closure of the duct but there are studies suggesting
that early, liberal fluid intakes are associated with a
higher incidence of PDA

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Medical Therapy - Indomethacin
 Indications
– Closure of persistent patent ductus arteriosus
 Contraindications and Precautions
– Anuria, severe oliguria (<0.5-1.0 ml/kg/hour)
– Serum creatinine
– Thrombocytopaenia
– Bleeding phenomena
– Necrotising enterocolitis
– Known hypersensitivity to indomethacin

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 Possible Adverse Effects
– Renal impairment
– Gastrointestinal dysfunction (abdominal
distension, gastrointestinal bleeding, necrotising
enterocolitis, gastric perforation, gastric ulceration)
– Platelet dysfunction and bleeding tendency
 Special Considerations
– Rapid infusions of intravenous indomethacin have
been associated with significant reductions in
cerebral blood flow
– Careful monitoring of gastrointestinal and renal
status is required during a course of therapy

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Surgery
 If PDA is still clinically significant after
indomethacin
 If indomethacin is contraindicated

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Echocardiography
 The best way to determine
– the presence of a duct
– the size of the duct
– the haemodynamic significance of a duct
– Echocardiography permits quantification of
effects on heart
– Ventilation parameters proxy for effect on
lungs
– Presence of duct does not mean it has to
be treated

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 Other benefits of ECHO
–Identification of structural
abnormalities
–Other cardiac problems
–Effusions
–Masses
–Assessment of other structures
–Line position

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The presence & size of the duct
 Determined best by the demonstration of flow between
aorta and main pulmonary artery (MPA)
 Also by a pattern of disturbed diastolic flow in the MPA
 Duct is most easily seen in the parasternal short axis and
the "ductal" views
 Absolute quantification of its diameter is the best way to
determine its presence or absence
 Duct is measured at its narrowest point
 Duct is most easily seen with colour Doppler and this is the
mode in which the measurement is taken

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Sometimes, the views are difficult - even with colour. Placing a
Doppler probe on the main pulmonary artery will show
disturbance of diastolic flow in the MPA if there is a duct with a
significant left-to-right shunt

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The size of the left atrium
 Left atrial enlargement signifies increased pulmonary
venous return because of left-to-right ductal shunting
 Reference measure is the ratio of the LA to aorta at the
level of the aortic valve (the LA:Ao ratio)
– Preterm – 0.84-1.4
– Term – 0.95 – 1.38
 LA:Ao ratio >1.4:1 indicates a moderate shunt
 The aorta does not enlarge with even extremely large PDA
so it is a useful measurement which allows for different
sized babies

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The size of the left ventricle
 LV enlarge as cardiac output increases with both
increased pulmonary venous return and with
increased diastolic run-off from the systemic
circulation
 There are subjective measures of this
– "paired eyeball test“
– the presence of mitral regurgitation as the mitral valve
ring dilates
 Objective measurements
– the left-ventricular end-diastolic dimension
– (LVEDD) :Ao ratio

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Descending aortic flow in diastole
 The presence
of a
significant
ductal shunt
results in
diastolic run-
off to the
pulmonary
circulation
 This will
result in flow
which is
retrograde in
the
descending
thoracic aorta
beyond the
duct during
diastole

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Ductal size
 helps to evaluate haemodynamic significance
 As diameter increases, so too does the
amount of flow which occurs
 Ducts which are more than 2mm in diameter
on colour Doppler are haemodynamically
significant
Flow in other organ blood vessels
 Disturbed flow patterns may be seen in brain,
kidney, and gut vessels as an effect of a
significant duct

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 None of these measures stands alone in
determining which ducts require treatment
 Other factors which influence the decision
include
– the gestational age and size of the baby
– the postnatal age of the baby
– the requirement for respiratory or cardiovascular
support
– symptoms attributable to a duct -
– hypotension
– pulmonary haemorrhage
– congestive heart failure
– poor growth

24. How good is clinical examination at
detecting a significant patent ductus
arteriosus in the preterm neonate?

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 DS Urquhart and RM Nicholl - Park Hospital, Watford Road,
Harrow, Middlesex. Archimedes Date submitted:16th January
 Three part question -
In a [ventilator dependant neonate of very low birth weight
(<1000g)] [how good is clinical examination] at [detecting patent
ductus arteriosus]?
 Search strategy: PubMed, Cochrane Library, SUMSearch
 Search outcome: Three papers found in PubMed
– Kupferschmid C et al,1988 - 47 babies
1. Cases: 29 with PDA
2. Controls: 29 without PDA
– Skelton R et al, 1994 -55 babies <1500g studied in the first 7
days of life
– Davis P et al, 1995 100 babies <1750g studied between day
3 and day 7 of life

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Clinical bottom line
 Clinical evaluation of PDA, either by
auscultation or by palpation of pulses, is
of limited value (with likelihood ratios
between 0.3 and 6)
 In the extremely low birthweight neonate,
Doppler flow echocardiography is
required to confidently rule in or rule out
the diagnosis of PDA