Comparison of monophasic versus biphasic cardioversion for atrial fibrillation

Background

Electrical cardioversion (CV) of patients with atrial fibrillation (AF) is a current practice. Recent data suggest that biphasic waveform shocks are more effective than monophasic ones for transthoracic CV, but the optimal protocol has not been defined.

Objective

To determine the rate of CV success comparing biphasic versus monophasic waveform energies; which is more effective to achieve cardioversion at initial shock and to access the cumulative energy used by each waveform energy.

Methods

We conducted a prospective, randomized study of 43 patients with atrial fibrillation during an 18-month period. Success rates of CV with a defibrillator using monophasic waveform energy with a sequential energy of 200 J–300 J–360 J (Group 1) and using biphasic waveform energy with a sequential energy of 120 J–150 J–200 J (Group 2) were randomly compared. If the maximum energy used by one group did not achieve CV success, a crossover to the maximum energy of the other group was performed.

Results

The study population consisted of 22 patients in Group 1 and 21 patients in Group 2 with similar baseline characteristics. The rate of CV success was 95.5% in Group 1 and 85.5% in Group 2 (P = not significant). Group 1 achieved success at initial shock in 95.5% and Group 2 in 57.1% (P = 0.27). The mean cumulative energy was 200 J in Group 1 and 203 ± 135 J in the biphasic waveform group (P = 0.078).

Conclusion

In this study, AF cardioversion using biphasic waveform energy was less effective than a monophasic pulse. This result could be attributed to the initial energy of 200 J used by the monophasic group.