Cryoablation for Perinodal Arrhythmia Substrates in Patients With Congenital Heart Disease and Displaced Atrioventricular Conduction Systems.

OBJECTIVES: The purpose of this study was to assess the safety and efficacy of cryoablation for perinodal substrates in patients with congenital heart disease (CHD) and a displaced atrioventricular (AV) conduction system or an AV conduction system location that was difficult to predict.

BACKGROUND: Catheter ablation for perinodal arrhythmias in patients with CHD may incur higher risks due to unconventional or difficult to predict locations of the AV conduction system. Cryoablation carries theoretical advantages for such patients but has not been studied in this setting.

METHODS: A total of 35 patients with CHD underwent cryoablation for perinodal substrates at the Montreal Heart Institute between 2006 and 2016. Ten of these patients, age 33 ± 13 years, 60% male, had AV conduction systems that were displaced or of uncertain location and underwent cryoablation (6-mm electrode-tip catheter) for 12 perinodal arrhythmias: AV nodal re-entrant tachycardia (n = 4), non-automatic focal atrial tachycardia (n = 4), septal intra-atrial re-entrant tachycardia (n = 3), and para-Hisian automatic focal atrial tachycardia (n = 1). Four patients had single-ventricle physiology and had undergone Fontan palliation (3 atriopulmonary and 1 intracardiac total cavopulmonary connection), 4 underwent repair of AV septal defects, 1 had congenitally corrected transposition of the great arteries (TGA), and 1 had TGA with a Mustard baffle.

RESULTS: Cryoablation was acutely successful in 9 of 12 targeted arrhythmias (75%) with no procedural complication. Crossover to radiofrequency ablation successfully eliminated the remaining 3 arrhythmias at sites deemed safe by cryoablation, with no complication. Over a follow-up period of 26 (interquartile range: 15 to 64) months, 1 of 9 successfully cryoablated arrhythmias recurred.

CONCLUSIONS: Cryoablation is feasible, safe, and moderately effective for perinodal arrhythmia substrates in patients with various forms of CHD associated with AV conduction systems that are displaced or in locations that cannot be reliably predicted.