Objective To study the circumstances and medical profile of out-of-hospital sudden cardiac arrest (SCA) patients in whom resuscitation was attempted by the ambulance service, and to identify causes of SCA in survivors and factors that influence resuscitation success rate.

Results Of 288 SCA patients in whom cardiopulmonary resuscitation (CPR) and advanced life support were applied, 47 (16%) were discharged alive from the hospital. Their mean (SD) age was 58 (11) years, 37 (79%) were men, and 24 (51%) had a history of cardiac disease. Acute myocardial infarction was diagnosed in 24 (51%) of the survivors; seven with and 17 without a history of cardiac disease. Ventricular fibrillation (VF) or ventricular tachycardia (VT) as the first documented rhythm was significantly positively associated with survival (odds ratio (OR) 5.7, 95% confidence interval (CI) 2.1 to 15.9). A time interval of less than four minutes between the moment of collapse and the start of resuscitation, and an ambulance delay time of less than eight minutes were significantly positively associated with survival (OR 3.3, 95% CI 1.3 to 8.6, and OR, 3.6, 95% CI 1.3 to 10.5, respectively). A history of cardiac disease was negatively associated with survival (OR 0.46, 95% CI 0.21 to 0.98).

Conclusions Acute myocardial infarction was the underlying mechanism of SCA in most of the survivors, especially in those without a history of cardiac disease. CPR within four minutes, an ambulance delay time less than eight minutes, and VT or VF diagnosed by the paramedics were positively associated with success.