Optimized First Phase Tilt in "Parallel-Series" Biphasic Waveform

• Published in: Journal of cardiovascular electrophysiology Vol. 8; no. 6; pp. 649 - 657
• Main Authors: YAMANOUCHI, YOSHIO, MOWREY, KENT A., KROLL, MARK W., BREWER, JAMES E., DONOHOO, ANN M., WILKOFF, BRUCE L., TCHOU, PATRICK J.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-06-1997
• Subjects: Animals; biphasic waveform; defibrillation; Defibrillators, Implantable; Electric Conductivity; Electric Countershock - methods; first phase tilt; parallel-series switching; small capacitor; Swine
• ISSN: 1045-3873; 1540-8167
• DOI: 10.1111/j.1540-8167.1997.tb01828.x

“Parallel‐Series” Biphasic Waveform. Introduction: A biphasic defibrillation waveform can achieve a large second phase leading‐edge voltage by a “parallel‐series” switching system. Recently, such a system using two 30‐μF capacitances demonstrated better defibrillation threshold than standard waveforms available in current implantable devices. However, the optimized tilt of such a “parallel‐series” system had not been defined.
Methods and Results: Defibrillation thresholds were evaluated for five different biphasic “parallel‐series” waveforms (60/15 μF) and a biphasic “parallel‐parallel” waveform (60/60 μF) in 12 anesthetized pigs. The five “parallel‐series” waveforms had first phase tilts of 40%, 50%, 60%, 70%, and 80% with second phase pulse width of 3 msec. The “parallel‐parallel” waveform had first phase tilt of 50% with second phase pulse width of 3 msec. The defibrillation lead system comprised a left pectoral “hot can” electrode (cathode) and a right ventricular lead (anode). The stored energy at defibrillation threshold of the “parallel‐series” waveform with first phase tilts of 40%, 50%, 60%, 70%, and 80% was 7.0 ± 2.1, 6.1 ± 2.8, 6.8 ± 2.8, 7.2 ± 2.9. and 8.4 ± 3.1 J, respectively. The stored energy of the “parallel‐series” waveform with a 50% first phase tilt was 16% less than the nonswitching “parallel‐parallel” waveform (7.3 ± 2.8 J, P = 0.006).
Conclusions: A first phase tilt of 50% maximized defibrillation efficacy of biphasic waveforms implemented with a “parallel‐series” switching system. This optimized “parallel‐series” waveform was more efficient than the comparable “parallel‐parallel” biphasic waveform having the same first phase capacitance and tilt.