Introduction: The amplitude spectral area (AMSA) of the ventricular fibrillation (VF) waveform serves to estimate the probability that an electrical shock could terminate VF and prompt return of spontaneous circulation (ROSC).
Hypothesis: We hypothesized that AMSA measured during CPR could enable more precise timing for effective shock delivery compared to current time-fixed shock delivery protocols.
Methods: A swine model of electrically-induced VF was used to compare three protocols for shock delivery in 12 pigs each: AMSA-Driven (AD), guided by an AMSA algorithm; Guidelines-Driven (GD), according to CPR guidelines; and Guidelines-Driven/AMSA-Enabled (GDAE), as per GD but allowing earlier shocks upon exceeding an AMSA threshold. Untreated VF was stratified into 6, 9, or 12 minutes.
Results: Shocks delivered using the AD, GD, and GDAE protocols were 21, 40, and 62, with GDAE delivering only two 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 (mmHg) was 16 [9-30], 10 [6-12], and 3 [-1-9] (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<0.05). The AD protocol delivered fewer unsuccessful shocks (i.e., less shock-burden) yielding less post-resuscitation myocardial dysfunction and higher 240-minute survival.
Conclusions: The AD protocol improved the time-precision for shock delivery resulting in longer CPR duration, higher coronary perfusion pressure, and higher AMSA prior to first shock delivery along with less shock-burden and higher survival rate compared to time-fixed, guidelines-driven, shock delivery protocols.