Comparison of biphasic and monophasic pulses: does the advantage of XXXX depend on the waveshape?

@entity1 @entity1457
With present implantable defibrillators, the ability to vary the defibrillation technique has been shown to increase the number of @entity1 suitable for transvenous system. As newer waveforms become available, the need for a flexible device may change. In addition, although it has been shown that the option of biphasic waveform may increase the defibrillation efficacy, this may depend upon the shape of the biphasic waveform used. Thirty @entity1 undergoing transvenous defibrillator implant were included in the study. In 20 @entity1 (group I), defibrillation efficacy of simultaneous monophasic, sequential monophasic, and biphasic waveform with 50% tilt was determined randomly. Similarly, in ten @entity1 (group II) testing of simultaneous monophasic shocks and biphasic waveforms with 65% and 80% tilt was performed in random order. The electrode system used consisted of two transvenous leads and a subcutaneous patch in all 30 @entity1 . In group I, 50% tilt biphasic waveform consistently provided similar or better defibrillation efficacy compared to monophasic waveforms (biphasic 7.5 +/- 5.1 joules vs simultaneous 17 +/- 7.8 joules, P < 0.01; and vs sequential 17 +/- 8.4 joules, P < 0.01). In group II, 65% tilt biphasic pulse required less energy for defibrillation as compared with simultaneous monophasic shocks (9.6 +/- 4.5 joules vs 15.6 +/- 5.1 joules, P = 0.04). No significant difference was observed in terms of defibrillation threshold between 80% tilt @entity1457 and simultaneous monophasic pulses (11.8 +/- 6 joules vs 15.6 +/- 5.1 joules, P = NS). @entity1457 with smaller tilt delivered using a triple lead system more uniformly improved defibrillation threshold over standard monophasic waveforms.
