Abstract 11957: An Ascending Ramp Second Phase Biphasic Waveform Has a Lower Defibrillation Threshold and Less Post-shock ST Elevation
Background: We have previously shown that a biphasic waveform with an 8 ms ascending ramp 1st phase and a 3.5 ms rectilinear 2nd phase has a lower defibrillation threshold (DFT) and releases less troponin I than a standard ICD truncated exponential biphasic waveform. The purpose of this study was to test whether an ascending ramp 2nd phase further reduces the DFT and post-shock cardiac damage estimated by post-shock ST elevation.
Methods and Results: In 6 pigs, DFTs were determined for 7 waveforms: a standard truncated exponential biphasic waveform with 60% tilt phase 1 and 50% tilt phase 2 (Fig 1,#1) and 6 biphasic waveforms with an 8 ms ascending ramp 1st phase and one of 3 rectilinear or ascending ramp 2nd phases generated by a new type of defibrillator circuit. The 3 rectilinear 2nd phases were: 1 ms, 125% the peak voltage of phase 1 (#2), 2 ms, same voltage as phase 1 (#3), 3 ms, half the voltage of phase 1 (#4). The 3 ascending ramp 2nd phases were: 2 ms, 125% the voltage of phase 1 (#5), 3 ms, same voltage as phase 1 (#6), 4.5 ms, half the voltage of phase 1(#7). Post-shock transient local injury was estimated from a bipolar right ventricular electrogram in 4 pigs. Phase 2 ascending ramp waveforms (#5 and #6) had the lowest DFTs, which were significantly smaller than for the truncated exponential waveform (Fig 1, mean and SD). Post-shock ST elevation was also lowest with ascending phase 2 waveforms (Fig 2).
Conclusions: Waveforms with an ascending ramp in both phases have a lower DFT and cause less cardiac damage as estimated from ST elevation than a truncated exponential waveform.
- © 2012 by American Heart Association, Inc.