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EXPERIMENTAL STUDY

Triphasic waveforms are superior to biphasic waveforms for transthoracic defibrillation

Experimental studies

Yi Zhang, MD, PhD^*, R. S. Ramabadran, MD, PhD^*, Kimberly A. Boddicker, MD^*, Imran Bawaney, MD^*, Loyd R. Davies, BS^*, M. Bridget Zimmerman, PhD^*, Scott Wuthrich, MSEE, Janice L. Jones, PhD and Richard E. Kerber, MD, FACC^*,*

^* Cardiovascular Center, College of Medicine, University of Iowa, Iowa City, Iowa, USA
Philips Medical Systems, Andover, Massachusetts, USA
Department of Physiology and Biophysics, Georgetown University, Washington, DC, USA
Department of Physiology at the Veterans Affairs Medical Center, Washington, DC, USA

Manuscript received October 29, 2002; revised manuscript received January 24, 2003, accepted March 7, 2003.

^* Reprint requests and correspondence: Dr. Richard E. Kerber, Department of Internal Medicine, University of Iowa Hospital, 200 Hawkins Drive, Iowa City, Iowa 52242, USA.
richard-kerber{at}uiowa.edu

OBJECTIVES: Our objective was to evaluate the efficacy of triphasic waveforms for transthoracic defibrillation in a swine model.

BACKGROUND: Triphasic shocks have been found to cause less post-shock dysfunction than biphasic shocks in chick embryo studies.

METHODS: After 30 s of electrically induced ventricular fibrillation (VF), each pig in part I (n = 32) received truncated exponential biphasic (7.2/7.2 ms) and triphasic (4.8/4.8/4.8 ms) transthoracic shocks. Each pig in part II (n = 14) received biphasic (5/5 ms) and triphasic shocks (5/5/5 ms). Three selected energy levels (50, 100, and 150 J) were tested for parts I and II. Pigs in part III (n = 13) received biphasic (5/5 ms) and triphasic (5/5/5 ms) shocks at a higher energy (200 and 300 J). Although the individual pulse durations of these shocks were equal, the energy of each pulse varied. Nine pigs in part I also received shocks where each individual pulse contained equal energy but was of a different duration (biphasic 3.3/11.1 ms; triphasic 2.0/3.2/9.2 ms).

RESULTS: Triphasic shocks of equal duration pulses achieved higher success than biphasic shocks at delivered low energies: <40 J: 38 ± 5% triphasic vs. 19 ± 4% biphasic (p < 0.01); 40 to <50 J: 66 ± 7% vs. 42 ± 7% (p < 0.01); and 50 to <65 J: 78 ± 4% vs. 54 ± 5% (p < 0.05). Shocks of equal energy but different duration pulses achieved relatively poor success for both triphasic and biphasic waveforms. Shock-induced ventricular tachycardia (VT) and asystole occurred less often after triphasic shocks.

CONCLUSIONS: Triphasic transthoracic shocks composed of equal duration pulses were superior to biphasic shocks for VF termination at low energies and caused less VT and asystole.

Abbreviations and Acronyms   CI   confidence interval   GEE   generalized estimating equations   LVEDP   left ventricular end-diastolic pressure   OR   odds ratio   PEA   pulseless electrical activity   VF   ventricular fibrillation   VT   ventricular tachycardia