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Three Part Question

In [Ventricular Fibrillation in humans] is [external defibrillation using biphasic or monophasic D/C shock] better [at restoring sinus rhythm]?

Clinical Scenario

You have just finished an unsuccessful cardiac resuscitation with an initial presenting rhythm of ventricular fibrillation. You wonder if one of the new Biphasic defibrillators would have increased the possibility of successful defibrillation when compared to your old monophasic device.

Search Strategy

Medline 1966-11/00 using the OVID interface.
(biphasic.mp OR monophasic.mp) AND (exp defibrillation OR exp electric counter shock OR cardioversion.mp)

Search Outcome

A total of 317 papers were identified of which 4 appeared relevant.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Greene HL et al, 1995, USA	171 patients undergoing electrophysiological studies for ventricular arrhythmias with induced VT and VF requiring external defibrillation. Monophasic vs biphasic	PRCT	Success of first shock in VT	85.2% (75/88) vs 97.6% (81/83)	Laboratory conditions for fresh arrhythmias
			Success of first shock in VF	78.6% (22/28) vs 100% (25/25)
Bardy G et al, 1996, USA	294 patients with induced VF/VT during implantation of cardioversion devices Monophasic vs biphasic	PRCT	Success of first shock	86% (143/166) vs 86% (144/167)	Laboratory conditions for fresh arrhythmias Results for VF and VT combined
Mittal S et al, 1999, USA	184 patients undergoing electrophysiological testing for ventricular arrhythmias producing an induced VF Monophasic vs biphasic	PRCT	Success of first shock	93% (80/86) vs 99% (97/98) (P=0.05)	Laboratory conditions for fresh arrhythmias
Schneider T et al, 2000, Germany	115 out of hospital VF cardiac arrests	Multicenter, unblinded, randomised controlled trial	Restoration of cardiac output (ROSC)	76% of patients with biphasic defibrillation had ROSC with 54% ROSC with monophasic defib (stat sig)	A variety of differing monophasic devices were used Crews were not blinded as to the type of defib output being used
			Survival to hospital discharge	No significant difference

Comment(s)

There is some "laboratory evidence" that biphasic defibrillation has higher first shock success rates for defibrillation of VF/VT. Use of biphasic devices in "real world" situations has a higher return of cardiac output but no overall survival advantage.

Clinical Bottom Line

The advantages of biphasic devices are currently mainly theoretical. No "real world" data exists that would mandate an immediate conversion to using biphasic devices.

References

1. Greene HL, DiMarco JP, Kudenchuk PJ et al. Comparison of monophasic and biphasic defibrillating pulse waveforms for transthoracic cardioversion. Am J Cardiology 1995;75(16):1135-39.
2. Bardy GH, Marchlinski FE, Sharma AD et al. Multicenter comparison of truncated biphasic shocks and standard damped sine wave monophasic shocks for transthoracic ventricular defibrillation. Circulation 1996;94(10):2507-14.
3. Mittal S, Ayati S, Stein KM et al. Comparison of a novel rectilinear biphasic waveform with a damped sine wave monophasic waveform for transthoracic ventricular defibrillation. JACC 1999;34(5):1595-601.
4. Schneider T, Martens PR, Paschen H et al. Multicenter, randomised, controlled trial of 150-J Biphasic shocks compared with 200-to-360-J Monophasic shocks in the resuscitation of out-of-hospital cardiac arrest victims. Circulation 2000;102(15):1780-87.