Comparison of monophasic and biphasic shocks for transthoracic cardioversion of atrial fibrillation

Abstract

Objective: To compare the efficacy of cardioversion in patients with atrial fibrillation between monophasic damped sine waveform and rectilinear biphasic waveform shocks at a high initial energy level and with a conventional paddle position. Design: Prospective randomised study. Patients and setting: 227 patients admitted for cardioversion of atrial fibrillation to a tertiary referral centre. Results: 70% of 109 patients treated with an initial 200 J monophasic shock were cardioverted to sinus rhythm, compared with 80% of 118 patients treated with an initial 120 J biphasic shock (NS). After the second shock (360 J monophasic or 200 J biphasic), 90% of the patients were in sinus rhythm in both groups. The mean cumulative energy used for successful cardioversion was 306 J for monophasic shocks and 159 J for biphasic shocks (p < 0.001). Conclusions: A protocol using monophasic waveform shocks in a 200-360 J sequence has the same efficacy (90%) as a protocol using rectilinear biphasic waveform shocks in a 120-200 J sequence. This equal efficacy is achieved with a significantly lower mean delivered energy level using the rectilinear biphasic shock waveform. The potential advantage of lower energy delivery for cardioversion of atrial fibrillation needs further study.

Crystals in the heart

“…1 In this sense the study's outcome is similar to that of the study reported by Page and colleagues, 2 who showed that for cardioversion of atrial fibrillation (AF), ''a biphasic shock waveform has greater efficacy, requires fewer shocks and lower delivered energy, and results in less dermal injury than a monophasic shock waveform''. Although a multicentre international study the number of patients recruited was less than that in Scholten's study population.…”

“…1 However, there is evidence in this study and elsewhere to suggest that a biphasic defibrillation waveform is ''better'' than monophasic. [2][3][4][5] The sense that this should be so may be engendered by the past experience of electrophysiologists with ventricular defibrillators and the decrease in defibrillation threshold that was seen with the advent of biphasic shock waveforms in these devices.…”

Part 8: Adult Advanced Cardiovascular Life Support

“…377 Cardioversion with monophasic waveforms should begin at 200 J and increase in stepwise fashion if not successful (Class IIa, LOE B). [372][373][374] Monomorphic VT (regular form and rate) with a pulse responds well to monophasic or biphasic waveform cardioversion (synchronized) shocks at initial energies of 100 J. If there is no response to the first shock, it may be reasonable to increase the dose in a stepwise fashion.…”

“…[372][373][374][375][376] If the initial shock fails, providers should increase the dose in a stepwise fashion.…”

Part 6: Electrical Therapies

“…[187][188][189][190][191] If the initial shock fails, providers should increase the dose in a stepwise fashion. Cardioversion of adult atrial flutter and other supraventricular tachycardias generally requires less energy; an initial energy of 50 J to 100 J is often sufficient.…”