The Impact of Double Sequential Shock Timing on Outcomes During Refractory Out –of-Hospital Cardiac Arrest

Abstract

BackgroundAnimal studies suggest the efficacy of double sequential external defibrillation (DSED) may depend on the interval between the two shocks, or “DSED interval”. No human studies have examined this concept. ObjectivesTo determine the relationship between DSED interval and termination of ventricular fibrillation (VFT), return of spontaneous circulation (ROSC), survival to hospital discharge, and favourable neurological status (MRS < 2) for patients in refractory VF. MethodsWe performed a retrospective review of adult (≥18 years) out-of-hospital cardiac arrest between January 2015 and May 2022 with refractory VF who received ≥1 DSED shock. DSED interval was divided into four pre-defined categories. We examined the association between DSED interval and patient outcomes using general estimated equation logistic regression or Fisher's exact test. ResultsAmong 106 included patients, 303 DSED shocks were delivered (median 2, IQR 1-3). DSED intervals of 75-125 msec (OR 0.39, 95% CI 0.16-0.98), 125-500 msec (OR 0.36, 95% CI 0.16-0.82), and >500 msec (OR 0.27, 95% CI 0.11-0.63) were associated with lower probability of VF termination compared to <75 msec interval. DSED interval of >75 msec was associated with lower probability of ROSC compared to <75 msec interval (OR 0.37, 95% CI 0.14-0.98). No association was noted between DSED interval and survival to hospital discharge or neurologic outcome. ConclusionsAmong patients in refractory VF a DSED interval of less than 75 msec was associated with improved rates of VF termination and ROSC. No association was noted between DSED interval and survival to hospital discharge or neurologic outcome.