Biphasic low energy internal cardioversion of atrial fibrillation induced during electrophysiologic study

Background. Atrial fibrillation is observed in 10% of electrophysiological studies. Previous studies have shown the efficacy of biphasic low energy in ternal cardioversion to restore sinus rhythm. We studied the efficacy and s afety of low energy internal cardioversion and the biphasic curver, in sust ained atrial fibrillation (> 15 min) during electrophysiologic procedures. Material and methods. From January 1997 to August 1998, 320 patients underw ent an electrophysiological study. An internal cardioversion was done on th ose patients who developed sustained atrial fibrillation. We delivered biph asic shocks between electrodes-catheters positioned in the right atrium and the coronary sinus. Increasing energy was applied until restoration of sin us rhythm or a maximum of 10 joules were achieved with no result. A right v entricle electrode was used to synchronize the V wave and for temporary pac ing. Results. Thirty one episodes of sustained atrial fibrillation were observed in 26 patients (1,23 episodes/patient) and a mean of 2,58 internal cardiov ersions were applied per every patient. Sinus rhythm was restored in twenty three patients. The mean energy delivered was 4.1 joules. The mean time fo r the recovery was 3,200 ms. Temporary pacing was used in 16% of the patien ts for up to 1 minute. No AV blocks were observed. Conclusions. Internal cardioversion successfully restored sinus rhythm in 8 8.5% of the patients who presented sustained atrial fibrillation (88.5%). T emporary pacing was necessary for the treatment of postsinus shock pauses.