A significant increase in the prevalence of sudden cardiac arrest (SCA) with non-shockable rhythm (NSR) has been reported. Factors associated with NSR and the mode to the return of spontaneous circulation (ROSC) may help for a better understanding.

We aimed to describe the frequency, characteristics and outcome of NSR related SCA in the community.

In this prospective ongoing multicentre population-based registry (6.7 million inhabitants), data from all SCA were analyzed. Medical records for each SCA were reviewed by two cardiologists to identify aetiology and associated conditions.

Among the 3,028 SCAs admitted alive out of a total of 18,622 out-of-hospital cardiac arrests from May 2011 to May 2016, 2,904 patients had available information regarding initial rhythm. Among them, 1,314 patients (45.3%) presented with NSR: 1,109 (38.2%) cases with asystole, 197 (6.8%) with pulseless electrical activity and 8 (0.3%) with high degree atrioventricular block. NSR cases were older (60.6 vs. 57.4 years, P<0.001), with greater proportion of females (34.9 vs. 19.2%, P<0.001) and less proportion of family history of CAD or SCA. Proportion of symptoms prior to the SCA was higher among patients with NSR (74.3 vs. 64.9%, P<0.001) but chest pain was lower (24.0 vs. 43.3%, P<0.001). Survival rate was much lower in NSR cases (7.2 vs. 42.3%, P<0.001). Among the 1,314 NSR cases, 1,022 (77.8%) did not require external defibrillation although a majority (91.7%) received adrenaline during resuscitation. In this subgroup, main identified cardiac cause was acute coronary syndrome (45.3%), followed by chronic CAD (27.1%), structural non-ischemic heart disease (22.4%), and non-structural heart disease (5.2%).

Initial NSR is encountered in almost half of SCA cases admitted alive; mostly occurs in older patients with higher proportion of females. Over three quarters of these cases did not require external defibrillation prior to ROSC.