Epidemiology and outcome of emergency medical service witnessed out-of-hospital-cardiac arrest by prodromal symptom: Nationwide observational study.

BACKGROUND: Although emergency medical service- (EMS-) witnessed out-of-hospital-cardiac arrest (OHCA) has a high survival rate and potential for prevention of progression to cardiac arrest, its characteristics and prodromal symptoms are not well known. The purpose of this study was to investigate the epidemiologic characteristics and outcome of EMS-witnessed OHCA by focusing on its prodromal symptoms.

METHODS: Population-based observational study was conducted for resuscitation-attempted EMS-witnessed adult OHCAs between 2012 and 2017. The prodromal symptoms were categorized according to the patients' chief complaints, which were checked in the EMS run sheets: no prodromal, respiratory, cardiac, neurologic, gastrointestinal (GI), or other symptom. If multiple complaints were checked, the patient was assigned to multiple groups. The OHCA characteristics and time from EMS scene arrival to cardiac arrest were investigated by symptom groups and presumed etiology of OHCA. The age- and sex-standardized survival rate and good neurological outcome rate were calculated for each symptom group.

RESULTS: Of 12,969 eligible OHCAs, 5,246 (40.5%) had prodromal symptoms, 1,410 (10.9%) had respiratory symptoms, 505 (3.9%) had cardiac symptoms, 1,987 (15.3%) had neurologic symptoms, and 541 (4.2%) had GI symptoms. Of 9,361 patients with cardiac etiology, 3,522 (37.6%) had prodromal symptoms, and patients with cardiac symptoms had the best rate of survival to discharge and good neurological outcome (42.7% and 38.2%, respectively). Of 3,424 patients with non-cardiac etiology, 1,651 (48.2%) had prodromal symptoms, and patients with respiratory symptoms had the best survival outcomes (19.0%). The age- and sex-standardized rates of good neurological outcome were better in patients with prodromal symptoms than in patients with cardiac etiology and no prodromal symptoms (cardiac, 30.4%; neurologic, 9.8%; respiratory, 8.9%; GI 7.3%; and no prodromal symptoms, 6.8%). EMS-witnessed OHCA occurred earlier in patients with no prodromal symptoms (5-9 minutes from EMS arrival) than in those with prodromal symptoms (10-14 minutes).

CONCLUSION: About 40% of EMS-witnessed OHCA patients had prodromal symptom before cardiac arrest. In cardiac etiology, patients with cardiac symptoms had the best rate of survival to discharge and good neurological outcome. Promoting public awareness of prodromal symptoms is needed to earn time for preparedness and prevention of progression to cardiac arrest.