Key result
A tuned defibrillation waveform resulted in similar delivered energy at the defibrillation threshold compared with a 50/50% fixed tilt waveform (10.5 vs 9.5 J; P=0.47).
Why the study?
Does a tuned defibrillation waveform improve defibrillation thresholds compared to a fixed 50/50% tilt waveform in patients with ICDs?
RCT (n=52)
random order
Does a tuned defibrillation waveform improve defibrillation thresholds compared to a fixed 50/50% tilt waveform in patients with ICDs?
Absolute Event Rate: 10.5% vs 9.5%
p-value: p=0.47
A tuned defibrillation waveform does not significantly improve defibrillation thresholds compared to a standard 50/50% fixed tilt waveform in patients with single-coil left pectoral ICDs.
Tuned waveforms do not reduce defibrillation energy versus fixed tilt; confirms equivalence and supports standard programming in single-coil ICDs.
BACKGROUND: All modern defibrillation systems use biphasic shock waveforms. Typically a fixed tilt waveform is used for implantable defibrillators (ICDs), but a tuned waveform with duration based on shock impedance may be superior based on theoretical calculations. OBJECTIVE: The objective of this study was to compare defibrillation efficacy of fixed tilt and tuned waveforms. METHODS: PROMISE was designed as a prospective, within-patient, randomized study of defibrillation thresholds (DFTs) comparing a tuned (assuming a 3.5 milliseconds membrane time constant) versus a 50/50% tilt waveform. All patients had a left pectoral implant (active can) and testing was performed with a single coil shocking configuration ("SVC coil OFF"). DFTs were measured in random order with a binary search method in 52 patients, using the high-voltage lead impedance to select the pulse widths for both waveforms. RESULTS: At the DFT, the tuned waveform had similar delivered energy (10.5 ± 6.3 vs 9.5 ± 5.5 J, P = 0.47), stored energy (13.6 ± 7.9 vs 11.3 ± 6.3 J, P = 0.06), peak current (7.5 ± 3.0 vs 6.8 ± 2.2 A, P = 0.09), and delivered voltage (451.0 ± 134.5 vs 411.5 ± 120.7 V, P = 0.05) compared with the 50/50% tilt waveform. CONCLUSION: The DFTs for 3.5-millisecond time constant based tuned and 50/50% tilt waveforms are similar using a single coil, left pectoral active can.
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Gold et al. (2012) conducted an RCT in Implantable defibrillator (ICD) placement (n=52). Tuned defibrillation waveform vs. 50/50% fixed tilt waveform was evaluated on Delivered energy at defibrillation threshold (J) (p=0.47). A tuned defibrillation waveform resulted in similar delivered energy at the defibrillation threshold compared with a 50/50% fixed tilt waveform (10.5 vs 9.5 J; P=0.47).
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