Serum troponin I and myoglobin after monophasic versus biphasic transthoracic shocks for cardioversion of persistent atrial fibrillation.

This study compared the effects of standard monophasic versus biphasic direct current shocks for cardioversion of atrial fibrillation (AF) on the release of cardiac troponin I (cTnI) and myoglobin (Myo). We randomized 48 patients with persistent AF (mean age = 61.4 +/- 10.7 years, 33 men) to monophasic (45.2%) or biphasic (54.8%) cardioversion. Plasma concentrations of cTn1 and Myo were measured before, and 6 and 24 hours after the procedure. Cardioversion was significantly more effective (88% vs 100%, P < 0.04) and required less energy (348.1 +/- 254.1 vs 187.6 +/- 105.3 J; P < 0.001) in the biphasic than the monophasic group. A significant increase in mean plasma cTnI concentration over 24 hours (0.23 +/- 0.18 vs 0.41 +/- 0.37 ng/mL, P < 0.04), and mean Myo concentration were recorded in the monophasic group over the first 6 hours following the procedure (38.2 +/- 14.2 vs 221.9 +/- 51.3 ng/mL, P < 0.001), whereas no significant increase was observed in the biphasic group. Increases in cTnI and Myo in the monophasic group correlated closely with the cumulative energy delivered (Spearman correlation coefficient r = 0.58, P = 0.004 for Myo and r = 0.67, P < 0.001 for cTnI). In addition, there was a positive correlation between cumulative cardioversion energy load and increase in Myo and cTnI indexed with left ventricular mass (r = 0.45, P < 0.02 for Myo and r = 0.47, P = 0.01 for cTnI). It is concluded that in cardioversion of AF, biphasic are more effective than monophasic and may cause less myocardial injury.