Key result
The low-tilt biphasic 8/4-ms waveform was significantly more likely to successfully defibrillate ventricular fibrillation than standard tilted biphasic waveforms (OR 122.3; 95% CI 32.5-460.2; P<0.001).
Why the study?
Does a low-tilt biphasic waveform improve defibrillation efficacy compared to standard tilted biphasic waveforms in a porcine model of ventricular fibrillation?
Does a low-tilt biphasic waveform improve defibrillation efficacy compared to standard tilted biphasic waveforms in a porcine model of ventricular fibrillation?
Effect estimate: OR 122.3 (95% CI 32.5, 460.2)
p-value: p=<0.001
Low-tilt biphasic waveforms demonstrate significantly higher defibrillation efficacy with comparable safety to standard tilted biphasic waveforms in a porcine model of ventricular fibrillation.
Hypothesis-generating for low-tilt biphasic defibrillation; human trials needed before any clinical consideration.
BACKGROUND: Commercially available implantable defibrillators utilize a high-tilt waveform. Studies in atrial fibrillation and transthoracic defibrillation of ventricular fibrillation (VF) have shown improved defibrillation efficacy using low-tilt (LT) waveforms. We investigated the feasibility, efficacy, and safety of a LT waveform in the transvenous defibrillation of VF and hypothesized that it would be more efficacious than standard tilted biphasic (STB) waveforms. METHODS AND RESULTS: The investigation was performed in four phases in a porcine model: an efficacy study of LT monophasic waveforms (n = 9), an efficacy study of LT biphasic waveforms (n = 9), a comparison study between the most successful LT waveforms and clinically available STB waveforms (n = 15), and a safety study (n = 9). A total of 1,056 shocks were delivered (phase 1: 288, phase 2: 288, phase 3: 480). The LT biphasic 8/4-ms waveform was significantly more likely to successfully defibrillate than the LT monophasic and STB waveforms with an odds ratio of 122.3 (95% confidence interval: 32.5, 460.2, P < 0.001). The calculated defibrillation threshold (E50) for the LT 8/4-ms waveform was 12.7 J compared to 43.5 J and 45.5 J for STB waveforms 6/6 ms and 8/4 ms, respectively, and 47.7 J for LT 12-ms waveform. The LT 8/4-ms waveform had no lasting detrimental effect on cardiac function, and any transient hemodynamical or biochemical changes observed were comparable to those observed with STB waveforms. CONCLUSION: LT waveforms are effective and appear safe in transvenous defibrillation in a porcine model of VF. The LT biphasic 8/4-ms waveform is more efficacious than conventional waveforms.
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Bennett et al. (2013) studied Ventricular fibrillation (n=42). Low-tilt (LT) waveforms vs. Standard tilted biphasic (STB) waveforms was evaluated on Successful defibrillation (OR 122.3, 95% CI 32.5, 460.2, p=<0.001). The low-tilt biphasic 8/4-ms waveform was significantly more likely to successfully defibrillate ventricular fibrillation than standard tilted biphasic waveforms (OR 122.3; 95% CI 32.5-460.2; P<0.001).
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