Biphasic vs. Monophasic Shock Waveform for Conversion of Atrial Fibrillation. The Results of an International Randomized, Double-Blind Multicenter Trial - BiCard
The goal of this study was to assess the safety and efficacy of biphasic shocks compared with that of monophasic shocks for cardioversion of atrial fibrillation (AF).
Patients Enrolled: 203
203 patients (mean age 65 years, mean left atrial diameter 4.8 cm) were randomly assigned to undergo transthoracic cardioeversion of AF with either a monophasic (107) or biphasic (96) shock using anterior-posterior electrodes. The investigators were blinded to the type of wave-form being used. A step-up protocol of 100, 150, 200 J was used in both groups. The fourth shock was 360 J in the monophasic group and 200 J in the biphasic group. If cardioeversion was unsuccessful, the patient crossed over to the alternative waveform, at maximum output.
Biphasic shocks restored sinus rhythm significantly more often than monophasic shocks at 100 J (60 vs. 22%), 150 J (77 vs 44%) and 200 J (90 vs. 53%). After the fourth shock, there was not a significant difference in the cumulative success rate (91% biphasic vs. 85% monophasic). Fewer shocks were needed to restore sinus rhythm with the biphasic that with the monophasic waveform (1.7 vs. 2.8), and less total energy also was needed (217 vs. 548 J). Dermal injury was less common after the biphasic than after the monophasic shocks (17 vs. 41%).
Compared to the monophasic shocks, biphasic shocks allow the restoration of sinus rhythm with fewer shocks, less total energy and with a lower risk of dermal injury. It is interesting to note that even in the biphasic group, cardioverstion was ineffective in approximately 10% of patients. In these patients, 1mg of ibutilide lowers the defibrillation energy requirement, greatly increasing the probability of successful cardioversion with another 200 J biphasic shock.
Page RL, Kerber RE, Russell JK, et al., for the BiCard Investigators. Biphasic vs. Monophasic Shock Waveform for Conversion of Atrial Fibrillation. The Results of an International Randomized, Double-Blind Multicenter Trial. J Am Coll Cardiol 2002; 39:1956-63.
Keywords: Electric Countershock, Probability, Sulfonamides
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