[Electrical cardioversion for atrial fibrillation: advantages of the transthoracic biphasic method].

Background: The purpose of this study was to evaluate efficacy and safety of biphasic shock for atrial fibrillation cardioversion to sinus rhythm. A second endpoint was to evaluate myocardial damage by means of cardiac troponin I dosage.

Methods: We studied 164 patients, with drug-resistant atrial fibrillation (208 episodes). Group A patients underwent biphasic shock normalized with respect to weight: 50 J (weight < 60 kg), 70 J (weight 61-84 kg) and 100 J (weight > 84 kg; the second and third shocks were 2 and 3 times higher than the first. Group B underwent sequential monophasic shock of 200, 300 and 360 J. Troponin I was evaluated at baseline, and 6, 12 and 24 hours after cardioversion.

Results: Total efficacy was 92% for biphasic shock and 89% for monophasic shock. First-shock efficacy with biphasic waveform (57.3%) was significantly greater than with first monophasic waveform (21.5%) (p = 0.000). Cardiac troponin I increased from 0.4 +/- 1.1 to 0.8 +/- 2.2 compared to a normal value of 2 ng/ml.

Conclusions: For transthoracic cardioversion of atrial fibrillation, biphasic shock has a greater efficacy requiring less energy compared to monophasic shock. Normal mean values of cardiac troponin I proved the absence of myocardial damage.