Biphasic waveform cardioversion as an alternative to internal cardioversion for atrial fibrillation refractory to conventional monophasic waveform transthoracic shock

External transthoracic electrical cardioversion for It termination of atrial fibrillation (AF) is among the most frequently performed and effective cardiovascular procedures.(1-4) It has been estimated that overall success is about 90%.(1,2) However, 2 types of treatment failures are observed. The first is transient termination of AF with subsequent early recurrence (so-called "immediate" or early recurrence of AF). The second is complete inability to cardiovert AF despite using both the highest available energy and a presumably optimum cardioversion vector. This latter failure may be overcome in some cases by modifying electrode position, by use of pharmacologic reduction of defibrillation threshold, or by undertaking an internal cardioversion procedure.(5) Recently, however, based on experience with implantable biphasic waveform cardioverter-defibrillators, the greater effectiveness of biphasic transthoracic waveform shocks (compared with previously conventional monophasic cardioversion waveforms) has been established in the setting of life-threatening ventricular tachyarrhythmias.(6-8) Further, by extension of these observations, the application of biphasic waveforms in the setting of elective transthoracic AF cardioversion has become increasingly accepted in clinical practice. In this study, we examined whether biphasic waveform shock offered sufficient additional benefit as to obviate the need for internal transcatheter cardioversion in patients who were being considered for this procedure because of failure of conventional monophasic waveform. cardioversion.