BIPHASIC SHOCKS ARE SUPERIOR TO MONOPHASIC FOR HUMAN
TRANSTHORACIC DEFIBRILLATION. SC Faddy*, J Powell, JC Craig. Cardiology Department, St Vincent's
Hospital, Sydney. Transthoracic defibrillation is the lifesaving treatment
for ventricular fibrillation (VF) and haemodynamically unstable ventricular
tachycardia (VT). Numerous clinical
trials have demonstrated the superiority of biphasic waveforms over monophasic
for internal defibrillation. In
comparison, only a few, small studies have been performed comparing these
waveforms for transthoracic defibrillation.
Monophasic damped sine and truncated exponential waveforms remain the
standard for external defibrillators. Methods: A
systematic review was performed of all studies comparing biphasic and monophasic
waveforms for transthoracic defibrillation.
Studies were included on the basis of methodological quality, suitable
study populations, specific interventions and relevant outcome measures. Data from relevant primary studies were
pooled in a meta analysis. Results: 200J
biphasic waveforms defibrillate with greater efficacy than 200J monophasic
(RR=1.10, 95%CI: 1.03 - 1.17). Efficacy
equivalent to that of a 200J monophasic shock can be achieved with biphasic
shocks of 130J (RR=0.99), 95%CI: 0.93-1.05) and 115J (RR=1.01, 95%CT:
0.95-1.08). The 130J biphasic shock
delivered on average 84.5J (95%CI: 82.8-86.2J) less energy than the 200J
monophasic shock to achieve equivalent efficacy while the 115J biphasic shock
delivered an average of 98.2J (95%CI: 97.1-99.4J) less energy. Biphasic shocks result in less remarkable ST
segment changes and faster return to sinus rhythm. Conclusion: Biphasic waveforms defibrillate with equal
efficacy at lower energies than standard 200J monophasic waveforms, and greater
efficacy than monophasic shocks of the same energy.
