Real-time ventricular fibrillation amplitude-spectral area analysis to guide timing of shock delivery improves defibrillation efficacy during cardiopulmonary resuscitation in swine

Abstract

Background--The ventricular fibrillation amplitude spectral area (AMSA) predicts whether an electrical shock could terminate ventricular fibrillation and prompt return of spontaneous circulation. We hypothesized that AMSA can guide more precise timing for effective shock delivery during cardiopulmonary resuscitation. Methods and Results--Three shock delivery protocols were compared in 12 pigs each after electrically induced ventricular fibrillation, with the duration of untreated ventricular fibrillation evenly stratified into 6, 9, and 12 minutes: AMSA-Driven (AD), guided by an AMSA algorithm; Guidelines-Driven (GD), according to cardiopulmonary resuscitation guidelines; and Guidelines- Driven/AMSA-Enabled (GDAE), as per GD but allowing earlier shocks upon exceeding an AMSA threshold. Shocks delivered using the AD, GD, and GDAE protocols were 21, 40, and 62, with GDAE delivering only 2 AMSA-enabled shocks. The corresponding 240- minute survival was 8/12, 6/12, and 2/12 (log-rank test, P=0.035) with AD exceeding GDAE (P=0.026). The time to first shock (seconds) was (median [Q1-Q3]) 272 (161-356), 124 (124-125), and 125 (124-125) (P < 0.001) with AD exceeding GD and GDAE (P < 0.05); the average coronary perfusion pressure before first shock (mm Hg) was 16 (9-30), 10 (6-12), and 3 (-1 to 9) (P=0.002) with AD exceeding GDAE (P < 0.05); and AMSA preceding the first shock (mV·Hz, mean±SD) was 13.3±2.2, 9.0±1.6, and 8.6±2.0 (P < 0.001) with AD exceeding GD and GDAE (P < 0.001). The AD protocol delivered fewer unsuccessful shocks (ie, less shock burden) yielding less postresuscitation myocardial dysfunction and higher 240-minute survival. Conclusions--The AD protocol improved the time precision for shock delivery, resulting in less shock burden and less postresuscitation myocardial dysfunction, potentially improving survival compared with time-fixed, guidelines-driven, shock delivery protocols.