DELAYED-EFFECTS OF RADIOFREQUENCY ENERGY ON ACCESSORY ATRIOVENTRICULAR CONNECTIONS

The purpose of this study was to determine the incidence and character istics of delayed effects on conduction through accessory atrioventric ular (AV) connections after apparently successful attempts at radiofre quency catheter ablation. Among 450 patients who had 471 accessory AV connections, the ablation procedure was unsuccessful in 26 patients (6 %), as defined by persistent conduction through the accessory AV conne ction 60 minutes after the final application of radiofrequency energy. In 6/26 unsuccesfully treated patients (24%), conduction through the accessory AV connection disappeared on a delayed basis. At least once during the ablation procedure, conduction through each of these 6 acce ssory AV connections was transiently eliminated for 10 seconds to 60 m inutes. Five of these accessory AV connections were left-sided and one was posteroseptal; one was concealed and five were manifest. Conducti on through the accessory AV connection disappeared on a delayed basis 6-18 hours after the ablation procedure in 4 patients, and at some tim e between 1-5 days or 1-60 days in the other 2 patients. In 2 patients , the delayed effect was only transient, while in 4 patients, conducti on through the accessory AV connections did not return during 5-23 mon ths of follow-up. In conclusion, up to 15% of patients who undergo an apparently unsuccessful attempt at radiofrequency ablation of an acces sory AV connection may later manifest a permanent loss of conduction t hrough the accessory AV connection.