2. Outline
• General consideration of SVT
• WPW and accessory pathway
• Catheter ablation of accessory pathway
• Multiple accessory pathway
• Special considerations in WPW and AVRT
• Issue not covered in today’s talk
Y.B. Liu
14. Incidence
• Overall incidence of accessory pathway (AP)
– 0.1-0.3% of general population
• First-degreee relatives of patients with AP
– 0.55%
• Incidence of multiple APs
– 3-20% in surgical series
– 5-18% in RFCA series
Y.B. Liu
15. Classification of Accessory Pathway
• Anatomy:
– Left (mitral annulus) vs. right (tricuspid
annulus)
• Electrophysiology:
– Decremental vs. nondecremental
– 8% of AP with decremental characteristics
• Direction: Anterograde vs. retrograde
– Concealed: retrograde conduction only
– Manifest: bi-directional conduction
(* anterograde only: uncommon)
Y.B. Liu
20. WPW syndrome
The diagnosis of WPW syndrome is
reserved for patients who have both
pre-excitation and tachyarrhythmias.
ACC/AHA/ESC Guidelines for the Management of Patients
With Supraventricular Arrhythmias; 2003
Y.B. Liu
22. Localization of Accessory
Pathway in WPW syndrome
• Transition zone
• R in lead I
• Positive or
Negative vector
of delta wave in
II, III, aVF
[PACE 1995; 18: 1469-1473]
Y.B. Liu
28. Localization of AP by retrograde P wave
during AVRT
Anterior
Anterior
III. aVF (+)
anterior
anterior
Lateral Lateral
lateral
lateral
poterior
poterior
J Am Coll Cardiol Poterior III. aVF (-) Poterior
1997;29:394–402
J Interv Card
Electrophysiol (2008)
22:55–63
Y.B. Liu
30. Intracardiac ECG for Localization of AP
• Localization of AV rings
• AV fusion: anterograde and retrograde
• VA interval, HH interval, HA time
• Zone of transition
–Pattern of initiation and termination
–VEST or VPC during SVT
–BBB during SVT
–AV block during SVT
Y.B. Liu
45. Endpoints of accessory pathway ablation
• Atrial pacing:
– No pre-excitation
– AV nodal decremental conduction (AH
prolongation in AEST)
• Ventricular pacing:
– Total VA block
OR
– VA nodal decremental conduction (be sure
site of Cs orifice and no SVT inducible)
Y.B. Liu
51. Definition of multiple accessory pathway
• APs separated by 1-3 cm
• Multistranded or broad-banded bypass
tracts as wide as 3 cm had been reported
Y.B. Liu
53. ECG Clues to Multiple APs
• Variations in pre-excited QRS morphology
(esp. during A fib.)
• Atypical patterns of pre-excitation
• Antidromic AVRT using a posterior septal
AP
• Orthodromic AVRT with changing
retrograde P wave morphology
• Antidromic AVRT with varying degrees of
antegrade fusion
Y.B. Liu
58. EP Evidence of Multiple APs
• Chang in pre-excited morphology at
different pacing cycle length and sites
• Differing pattern of antegrade and
retrogade conduction
• Varying patterns of retrograde atrial
activation sequence during AVRT or V
pacing or from orthodromic to antidromic
AVRT
• Appearance of an AP after AAD or
ablation
Y.B. Liu
62. Distribution
• R. free wall AP +R. posteroseptal AP
(manifest > concealed about 2: 1)
• 2 L. free wall
(concealed > manifest)
Y.B. Liu
63. Arrhythmias associated with multiple APs
• Orthodromic AVRT
• Antidromic AVRT
– 33% vs. 6%
• Atrial fibrillation
– More clinical AF
– More induced AF
– More AF after RV pacing and AVRT
• AP as a bystander
Sudden death?
Y.B. Liu
64. RFCA in multiple APs
• Longer procedure time
• Greater radiation time
• Higher recurrent rate
– per patient
– per AP
Dual AV nodal pathway, 10-20%
– Only 1 patient develop AVNRT
Y.B. Liu
67. WPW and Sudden Cardiac Death
• 0.15% to 0.39% over 3 to 10 yr follow-up
• In case with SCD, half of them is the first
manifestation of WPW
• Risk factors:
–Shortest pre-excited RR<250 ms
–Symptomatic tachycardia
–Multiple APs
–Ebstein’s anomaly
–Familial WPW
Y.B. Liu
69. Pharmacological Treatment of WPW
• Pre-excited tachycardia
– Adenosine used with caution
– Verapamil, diltiazem, digoxin: Class III
• Long-term therapy
– Propafenon: 69% effective; side effects:25%
– Sotalol
– Amiodarone: not superior to other AAD
– Single use of verapamil, diltiazem, digoxin: not
recommended
• Pill-in-the-Pocket
– Diltiazem 120 mg + propranolol 80 mg
– 32 ± 22 min
Y.B. Liu
74. Unusual connection: Mahaim fiber
The true Mahaim fiber is the nodofascicular or nodoventricular connection faithful
to the original pathologic description. Over time, the term became a generic
description for any pathway with slow decremental conduction properties.
Y.B. Liu
