Defibrillation Outcomes by Pad Placement for Initially Non-Shockable Out-of-Hospital Cardiac Arrest

Study Objective: Our objective was to determine the association between anterior-posterior (AP) and anterior-lateral (AL) pad placement and outcomes for patients with out-of-hospital cardiac arrest (OHCA) with an initial non-shockable rhythm requiring subsequent defibrillation. This observational cohort study included patients with OHCA treated by an emergency medical services (EMS) agency from July 2019 through June 2023. We included patients with initial non-shockable rhythms who subsequently developed a shockable rhythm and received EMS defibrillation. We compared outcomes between AP and AL placement. The primary outcome was the cumulative incidence in return of spontaneous circulation (ROSC) after defibrillation among those at-risk using competing risks regression, adjusting for confounding variables. We assessed secondary outcomes through multivariable logistic regression, including ROSC, ROSC at emergency department (ED) arrival, survival to admission, survival to discharge, and survival with cerebral performance category score ≤2. We included 109 patients, 69 with AP and 40 with AL. AP, compared to AL, had significantly higher cumulative incidence of subsequent ROSC (subdistribution hazard ratio 95% CI: 2.66 1.04-6.84). AP did not achieve statistically significant differences in odds (adjusted odds ratio 95% CI) of ROSC at any time (2.18 0.65-7.38), ROSC at ED arrival (1.11 0.26-4.72), or survival to admission (2.52 0.61-10.31). No patients with AL (0/40) survived to discharge (versus AP 3/69 4.3%), precluding multivariable analysis. Conclusion Larger studies on initial pad placement for patients suffering OHCA with initial non-shockable rhythms subsequently receiving defibrillation are necessary to determine whether AP or AL is the most optimal initial strategy.