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(Circulation. 2000;101:2968.)
© 2000 American Heart Association, Inc.

Basic Science Reports

Resuscitation After Prolonged Ventricular Fibrillation With Use of Monophasic and Biphasic Waveform Pulses for External Defibrillation

Charles T. Leng, MD; Norman A. Paradis, MD; Hugh Calkins, MD; Ronald D. Berger, MD, PhD; Albert C. Lardo, PhD; Kenneth C. Rent; Henry R. Halperin, MD, MA

From the Division of Cardiology (C.T.L., H.C., R.D.B., H.R.H.), Department of Medicine, The Johns Hopkins Medical Institutions, Baltimore, Md; the Department of Emergency Medicine (N.A.P.), Putnam Memorial Hospital, Bennington, Vt; and the Department of Biomedical Engineering (A.C.L., K.R., H.R.H.), Johns Hopkins University, Baltimore, Md.

Correspondence to Charles T. Leng, MD, The Johns Hopkins Hospital, Carnegie 568, 600 N Wolfe St, Baltimore, MD 21287. E-mail cleng{at}mail.jhmi.edu

Background—Survival after prolonged ventricular fibrillation (VF) appears severely limited by 2 major factors: (1) low defibrillation success rates and (2) persistent post-countershock myocardial dysfunction. Biphasic (BP) waveforms may prove capable of favorably modifying these limitations. However, they have not been rigorously tested against monophasic (MP) waveforms in clinical models of external defibrillation, particularly where rescue from prolonged VF is the general rule.

Methods and Results—We randomized 26 dogs to external countershocks with either MP or BP waveforms. Hemodynamics were assessed after shocks applied during sinus rhythm, after brief VF (>10 seconds), and after resuscitation from prolonged VF (>10 minutes). Short-term differences in percent change in left ventricular +dP/dt_max (MP -16±28%, BP +9.1±24%; P=0.03) and left ventricular -dP/dt_max (MP -37±26%, BP -18±20%; P=0.05) were present after rescue from brief VF, with BP animals exhibiting less countershock-induced dysfunction. After prolonged VF, the BP group had lower mean defibrillation thresholds (107±57 versus 172±88 J for MP, P=0.04) and significantly shorter resuscitation times (397±73.7 versus 488±74.3 seconds for MP, P=0.03).

Conclusions—External defibrillation is more efficacious with BP countershocks than with MP countershocks. The lower defibrillation thresholds and shorter resuscitation times associated with BP waveform defibrillation may improve survival after prolonged VF arrest.

Key Words: ventricular fibrillation • defibrillation waveform • resuscitation

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