An Ascending Ramp First Phase Biphasic Shock Defibrillates With Lower Energy And Causes Markedly Less Damage

Introduction: ICD shocks damage the heart and may increase mortality. Hypothesis: We tested the hypothesis that a biphasic shock with an ascending ramp as first phase (RAMP, Fig A) causes less damage than a standard biphasic truncated exponential shock (BTE, Fig B). Methods: Either a 20J RAMP or a 25J BTE was delivered through right ventricular (RV) and SVC electrodes in pigs. To be considered a successful experiment, the waveform had to defibrillate 2 VF episodes 5 min apart. Six successes were required for each waveform. A bipolar recording between a tip lead electrode and the RV coil was made for STT changes. Blood samples were drawn before the first shock and hourly for 6 hours after the second shock for troponin I levels. Histologic sections were taken near the RV coil. Results: RAMP shocks succeeded in 6 successive pigs, while BTE shocks failed in 8 pigs before 6 successes were achieved (Fig C). Troponin I after 6 hours was ~4 times greater with BTE than with RAMP shocks (Fig 4, P Conclusions: Thus, RAMP shocks defibrillate more reliably at a lower energy and cause markedly less damage as indicated by troponin I, ST elevation, and histopathology.