Prodromal symptoms of out-of-hospital cardiac arrests: a report from a large-scale population-based cohort study.

OBJECTIVE: Little is known about which symptoms are manifested before out-of-hospital cardiac arrest (OHCA). The objective of this study is to describe the prodromal symptoms of OHCA focusing on the onset of the symptom in relation of etiology of cardiac arrests, and to analyze the association between those symptoms and their outcomes after OHCA.
METHODS: This prospective, population-based cohort study enrolled all persons aged 18 years or older who had experienced OHCA of presumed cardiac and non-cardiac origin that were witnessed by bystanders or emergency medical system (EMS) personnel in Osaka from 2003 through 2004.
RESULTS: There were 1042 were presumed to be of cardiac origin and 424 of non-cardiac. Patients with non-cardiac origin were more likely to have prodromal symptoms than those with cardiac etiology (70.0% vs. 61.8%, p=0.003). Over 40% of OHCA regardless of etiology had displayed symptoms at least several minutes before their arrest (40.2% [259/644] in those of cardiac origin and 45.5% [135/297] in those of non-cardiac origin). As to cardiac origin, the most frequent prodromal symptom was dyspnea (27.6%), followed by chest pain (20.7%) and syncope (12.7%). For non-cardiac origin, the most frequent symptom was also dyspnea (40.7%), but chest pain was rarely presented (3.4%). Although, prodromal symptoms themselves were not associated with better neurological outcomes (adjusted odds ratio [AOR], 2.03; 95% confidence interval [CI], 1.00-4.13), earlier contact to a patient yielded better neurological outcomes (AOR per every one-minute increase, 0.90; 95% CI, 0.82-0.99).
CONCLUSIONS: Many of OHCA regardless of etiology have prodromal symptoms before arrest. Prodromal symptoms induced early activation of the EMS system, and may thus improve outcomes after OHCA.