Single shock endocavitary low energy intracardiac cardioversion of chronicatrial fibrillation

Background. Discomfort related to low-energy internal cardioversion (LEIC) represents a real problem in patients (pts) with atrial fibrillation (AF). The aim of our study was to verify if a single shock could restore sinus rh ythm (SR) with a lower discomfort for the pt. Methods. Thirty pts with chronic AF were randomized to receive a single 350 V shock (15 pts) or multiple shocks of increasing energy (15 pts). Three l eads were positioned, respectively, in the coronary sinus and in the latera l right wall for shock delivery, and in the right ventricular apex for R wa ve synchronization. Truncated, biphasic shocks were used. In the first grou p a single 350 V shock was directly delivered and a second 400 V shock was given only if SR has not been restored. In the second group, beginning at 5 0 volts the voltage was increased in steps of 50 volts until SR restoration . No patient was sedated. After each shock the pts were asked to rate their discomfort on a scale of 1 to 5 (1 = not perceived, 5 = severe discomfort) Results. SR was restored in all the subjects. In group 1 SR was obtained in 12/15 (80%) pts with the first 350 V(8.1+/-0.8 joules) shock, while the re maining 3 patients required the second 400 V (10.2+/-0.3 joules) shock. In group 2 the mean atrial defibrillation threshold was 346.7+/-1029.7 volts ( 8.+/-101.5 joules). Then discomfort score was 2.5+/-0.6 in group 1 and 3.3/-10.6 in group 2 (p < 0.01). Conclusions. A single shock of 350 V restores SR in the majority of pts wit h chronic AF; by use this new approach, LEIC is tolerated better than the m ultiple shocks step-up protocol.