American College of Cardiology - May 1, 2002, Volume 39, Number 9 (supplement B)

In recent clinical studies, electrical cardioversion of atrial fibrillation has been shown to be more effective and to require less energy if a rectilinear biphasic waveform is used instead of the traditional monophasic one. 

METHOD

To investigate this hypothesis, we prospectively randomized 40 patients (26 M, 14 F, age 58±16) affected by atrial fibrillation. 20 patients were treated with rectilinear biphasic shock (RBS) and 20 patients with monophasic shock (MS). Both groups were delivered with increasing energy levels (50 – 75 – 100 – 150 - 200 J for RBS and 100 – 150 – 200 – 300 - 360 J for MS). Rectilinear biphasic shocks, generated from a Biphasic M series (ZOLL Medical Corporation), consisted of a constant current 6ms first phase pulse followed by a truncated exponential 4ms second phase pulse; monophasic shocks were generated from ZOLL PD2000 (ZOLL Medical Corporation). In both groups, adhesive pads were in anterior/posterior position.

RESULTS

19/20 patients in group RBS (95%) and 17/20 patients in group MS (85%) achieved normal sinus rhythm. First shock efficacy was 68% in group RBS (13/19) and 52.9% in group MS (9/17). In patients with atrial fibrillation, first rectilinear biphasic shock achieved normal sinus rhythm in 68% of cases with less energy (50J) compored with first monophasic shock resulting in effective cardioversion in only 52% of patients with higher energy Ievel (1OOJ) and even higher in the rest of the group. To achieve normal sinus rhythm a Iower amount of energy (2450J vs 3900J) and a lower mean energy/patient (128.9J vs 229.4J) was delivered in the RBS group compared with the MS group, with a mean reduction in the energy/patient of 100J.

CONCLUSION

In atrial fibrillation, rectilinear biphasic transthoracic shock is more effective than monophasic shock and less energy is required, resulting in Iess post shock disfunction and shorter sedation.