RECURRENCE AND LATE BLOCK OF ACCESSORY PATHWAY CONDUCTION FOLLOWING RADIOFREQUENCY CATHETER ABLATION

Introduction: Many issues regarding the recurrence of accessory pathwa y conduction and the long-term outcome of late block of accessory path way conduction are still unknown or controversial. Methods and Results : Data from 217 patients who underwent an initially successful radiofr equency ablation of accessory pathways and 7 patients with late block of accessory pathway conduction following an initially unsuccessful ab lation were analyzed. During a mean followup of 19 +/- 11 months, acce ssory pathway conduction resumed in 21 (10%) of 217 patients following an initially successful ablation and in 6 (86%) of 7 patients with la te block of accessory pathway conduction (P < 0.01). After initially s uccessful ablations, the recurrence rates of accessory pathway conduct ion at 1, 3, and 6 months were 5.9%, 7.4%, and 11.3 %, respectively. A late electrophysiologic study at 6 months uncovered recurrence in onl y 1 of 124 asymptomatic patients, but failed to detect the late recurr ence in 2 patients in whom the accessory pathway conduction resumed af ter more than 6 months. Multivariate analysis revealed that independen t predictors for recurrence of accessory pathway conduction were conce aled accessory pathway, presence of transient effect of radiofrequency pulse, and more than 5 pulses required for initial cure. Accessory pa thway location, length of the tip electrode of the ablation catheter, and repeat radiofrequency pulses (''safety pulses'') after effective p ulses did not predict resumption of accessory pathway conduction. Conc lusions: After initially successful ablation, the recurrence rates of accessory pathway conduction at 1, 3, and 6 months were 5.9%, 7.4%, an d 11.3%, respectively. Late electrophysiologic testing had little prog nostic value in asymptomatic patients following successful ablation. A pplication of ''safety pulses'' did not prevent recurrence. Late block of accessory pathway conduction did not predict long-term efficacy.