Conversion From Initial Non-Shockable Rhythm to Shockable Rhythm During Resuscitation With a Public Access Defibrillator Compared With Initial Shockable Rhythm; Incidence and Survival Outcomes

Incidence of initial non-shockable rhythm during cardiac arrest is increasing and is associated with poorer outcomes. The aim of this analysis was to study non-shockable to shockable rhythm conversion treated using a public access defibrillator (PAD) and to study survival rates related to initial shockable rhythm. HeartSine PAD data were collected between October 2012 to May 2023. The dataset consisted of data downloaded from PADs, and data recorded in case report forms. Initial rhythm and conversion to shockable rhythm were determined. First shock success (FSS) was defined as the termination of the shockable rhythm for at least 5 seconds. Chi-squared test was applied to determine if there was difference in outcomes between those patients with: a shockable rhythm, non-shockable rhythm that converted to shockable, and non-shockable rhythm that did not convert to a shockable rhythm. Of the 6877 cases submitted initial shockable rhythm could be determined for 6736 cases. For the 30.5% (2053/6736) of cases with an initial shockable rhythm, patient outcome was reported for 1923, and 62.9% (1209/1923) survived to hospital admission. Incidence of initial non-shockable rhythm was 69.5% (4683/6736). Change to a shockable rhythm could be determined for 4664 cases and occurred in 5.0% (233/4664). A shock was delivered in 94.8% (221/233) of these cases. FSS could be determined for 165 cases. FSS was 85.5% (141/165). Patient outcome was reported for 87.6% (204/233) where 22.5% (46/204) resulted in survival to hospital admission. For the 95% (4431/4664) of non-shockable cases that did not convert to a shockable rhythm, patient outcome was reported for 82.2% (3644/4431), where 10.8% (395/3644) of patients survived to hospital admission.Thus, conversion from non-shockable to shockable rhythm had improved survival compared to patients who did not convert. Furthermore, when initial rhythm was shockable significantly higher survival to hospital admission was recorded.