Comparison of Fixed Tilt and Tuned Defibrillation Waveforms: The PROMISE Study


  • Clinical trial registration information: URL: Unique identifier: NCT00874445.

  • M. Gold reports honoraria and travel support from St. Jude Medical. J. Val-Mejias reports an educational grant from St. Jude Medical. M. Siddiqui received compensation from St. Jude Medical for participation on a speakers’ bureau. F. Cuoco reports no conflicts.

Michael Gold, M.D., Ph.D., Medical University of South Carolina, 25 Courtenay Drive, ART 7031 MSC 592, Charleston, SC 29425-5920, USA. Fax: +843-876-4990; E-mail:


Comparison of Defibrillation Waveforms. 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. (J Cardiovasc Electrophysiol, Vol. 24, pp. 323-327, March 2013)