Comparison of Biphasic and Monophasic Pulses: Does the Advantage of Biphasic Shocks Depend on the Waveshape?

Abstract

With present implantable defibrillators, the ability to vary the defibrillation technique has been shown to increase the number of patients 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 patients undergoing transvenous defibrillator implant were included in the study. In 20 patients (group I), defibrillation efficacy of simultaneous monophasic, sequential monophasic, and biphasic waveform with 50% tilt was determined randomly. Similarly, in ten patients (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 patients. 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 biphasic shocks and simultaneous monophasic pulses (11.8 +/- 6 joules vs 15.6 +/- 5.1 joules, P = NS). Biphasic shocks with smaller tilt delivered using a triple lead system more uniformly improved defibrillation threshold over standard monophasic waveforms.

Patient, Physician, and Procedural Factors Influencing the Use of Defibrillation Testing during Initial Implantable Cardioverter Defibrillator Insertion: Findings from the NCDR®

“…Since the early trials evaluating ICD therapy, defibrillation efficacy has greatly improved. Modern technology now includes devices with biphasic waveforms and pectoral active can systems that result in more effective defibrillation . In addition, devices now have a higher output, routinely delivering ≥35 Joules, also increasing the chance of effective defibrillation.…”

Impedance compensated biphasic waveforms for transthoracic cardioversion of atrial fibrillation: a multi-centre comparison of antero-apical and antero-posterior pad positions

“…Biphasic waveforms have been shown to be more efficient in terms of peak voltage and delivered energy than monophasic waveforms of equivalent duration both for endocardial atrial 2 and for ventricular defibrillation. [3][4][5][6] Transthoracic impedance (TTI) has been shown to be a determinant of atrial 7 and ventricular defibrillation 8 and is now widely accepted as an important predictor of success. 9 The new generation of external defibrillators have therefore been developed to deliver impedance compensated biphasic (ICB) waveforms.…”

ICD Leads:

“…In addition, antitachycardia pacing was integrated into third‐generation ICD devices that allowed painless termination of most episodes of monomorphic ventricular tachycardia 4–7 . The introduction of biphasic shocks in 1990 reduced the average energy requirement for ventricular defibrillation by approximately 5 J, further increasing the safety of implantation and device therapy 8–11 . From then on, defibrillator implantation with transvenous leads, initially aided by subcutaneous patch or array electrodes, became possible in nearly all cases, and practically eliminated the need for thoracotomy 12 .…”