Transthoracic cardioversion of atrial fibrillation - Comparison of rectilinear biphasic versus damped sine wave monophasic shocks

Background-Clinical studies have shown that biphasic shocks are more effect ive than monophasic shocks for ventricular defibrillation. The purpose of t his study was to compare the efficacy of a rectilinear biphasic waveform wi th a standard damped sine wave monophasic waveform for the transthoracic ca rdioversion of atrial fibrillation. Methods and Results-In this prospective, randomized, multicenter trial, pat ients undergoing transthoracic cardioversion of atrial fibrillation were ra ndomized to receive either damped sine wave monophasic or rectilinear bipha sic shocks. Patients randomized to the monophasic protocol (n=77) received sequential shocks of 100, 200, 300, and 360 J. Patients randomized to the b iphasic protocol (n=88) received sequential shocks of 70, 120, 150, and 170 J. First-shock efficacy with the 70-J biphasic waveform (60 of 88 patients , 68%) was significantly greater than that with the 100-J monophasic wavefo rm (16 of 77 patients, 21%, P<0.0001), and it was achieved with 50% less de livered current (11+/-1 versus 22+/-4 A, P<0.0001). Similarly, the cumulati ve efficacy with the biphasic waveform (83 of 88 patients, 94%) was signifi cantly greater than that with the monophasic waveform (61 of 77 patients, 7 9%; P=0.005). The following 3 variables were independently associated with successful cardioversion: use of a biphasic waveform (relative risk, 4.2; 9 5% confidence intervals, 1.3 to 13.9; P=0.02), transthoracic impedance (rel ative risk, 0.64 per 10-Omega increase in impedance; 95% confidence interva ls, 0.46 to 0.90; P=0.005), and duration of atrial fibrillation (relative r isk, 0.97 per 30 days of atrial fibrillation; 95% confidence intervals, 0.9 6 to 0.99; P=0.02). Conclusions-For transthoracic cardioversion of atrial fibrillation, rectili near biphasic shocks have greater efficacy land require less energy) than d amped sine wave monophasic shocks.