The efficacy and safety of catheter ablation of accessory pathways (AP) was studied in 79 children (age, 4-16 years), using DC shocks (n = 25) or radiofrequency energy (n = 54). All patients had documented arrhythmias including ventricular fibrillation in four. Organic heart disease was present in four patients. AP locations were left lateral (n = 36), posteroseptal (n = 36), right lateral (n = 8), Mahaim fibres (n = 2) and right anteroseptal (n = 6). Seven patients had multiple AP. One patient had a preexcitation which appeared secondary to an atrio-infundibular connection (Fontan procedure). The ablation site of concealed or overt AP was identified by retrograde or anterograde conduction mapping, respectively. A mean of 2.6 +/- 1 cathodal shocks (80-160 J) was delivered to 25 patients over 29 sessions, resulting in initial AP ablation in all. Fulguration was uncomplicated in all except in one patient (4%) who developed a secondary complete AV block post-ablation. During a follow-up period of 30-69 months, intermittent preexcitation recurred in two asymptomatic patients, but no significant tachycardia was inducible at late electrophysiological study, including under isoproterenol infusion. Radiofrequency energy was applied to 54 patients during 62 sessions, using 20-40 watts for 30-60 s. AP ablation was initially achieved in all patients using a median of three impulses, without significant immediate side-effects. Two patients (4%) developed a short episode of blurred vision possibly due to a microembolism. After discharge, the follow-up period was 10 +/- 5 months (range 1 to 24). All patients but one (98%) were asymptomatic without any drug therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

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