Determinants of muscular damage with external cardioversion of atrial fibrillation: Results of a randomized trial comparing biphasic with monophasic shock

Background. We want to compare the effects on muscular damage of the monophasic shock (M) with that of the new biphasic one (B) in patients (pts) undergoing external cardioversion (ECV) of atrial fibrillation (AF). Methods. All the pts admitted for ECV (n=171, age: 74±9, men: 68%) between 3/2001 and 6/2003 were randomized to B (Multipulse Biowave) or M. To stop AF, energy was delivered if necessary with stepwise increments until the highest value; in case of failure, pts crossed to ECV with the other waveform. Blood samples were collected to determine indexes of muscular damage. Results. After randomization, 90 pts were assigned to B and 81 to M. No differences existed between the two waveforms in efficacy (B: 88 vs M: 90%, p=.813). The energy delivered with the effective shock was lower with B (127±41 vs 229±99 J, p=.001), such as the total amount of delivered energy by weight (3±2 vs 4±3 J/Kg, p=.026). After ECV, indexes of muscular damage were altered only in pts treated with M (CPK - M: +200±75 vs B: -21±11 UI/L, p=.002; Myoglobin - M: +239±85 vs B: -2±11 ng/ml, p=.001). Multivariate models showed that both the increases for CPK and Myoglobin were positively related not only to the total amount of energy delivered (p=.001 in both cases) but also to the use of M (p=.038 and p=.041, respectively). No associations were noted with cardiac and systemic diseases and with variables related to AF. Conclusion. B has an efficacy comparable to M, but it is safer, because shocks need lower energy and so lower currents go through the patients.