Background: External, rectilinear biphasic cardioversion (RBC), as against monophasic cardioversion, requires lower energy and has been documented to be more effective in restoring sinus rhythm in atrial fibrillation (AF). There is, however, limited data on the optimal protocol of low energy RBC in atrial flutter (AFl) and regular atrial tachyarrhythmias (AT).
Methods and results: A prospective, single-center study was conducted, wherein 50 consecutive patients (mean age: 70.8 ± 8.7; 24 males) undergoing cardioversion of persistent or paroxysmal AFl or AT were randomized into two protocols of subsequent RBC shocks: 1) 10 J, 20 J, 50 J, 100 J, 200 J or 2) 20 J, 50 J, 100 J, 200 J. Initial energy was effective in 9/28 (32%) patients using Protocol 1 and in 12/22 (52%) patients using Protocol 2 (NS). In 9/12 patients with pacemakers, energy of 10 J or 20 J restored sinus or atrial-paced rhythm. Mean cumulative energy and number of shocks was 67 ± 70 J vs 64 ± 62 J (NS) and 2.0 ± 0.8 vs 1.6 ± 0.7 (p = 0.05) for both protocols, respectively. Mean successful energy was higher for AFl patients than for AT patients 66 ± 49 J vs 30 ± 19 J, p < 0.04. In approximately 25% of patients, conversion of AFl/AT into AF was observed after initial energy.
Conclusions: Low energy RBC is effective in 32-52% of patients with AFl/AT. Energy of 50 J is effective in 73% of patients and should be recommended as an initial energy in regular AT. Low energy RBC may be especially indicated in patients with pacemakers. (Cardiol J 2011; 18, 1: 33-38)