Objective: The purpose of this study was to identify factors associated with time delay to emergency medical services for patients with suspected ST-elevation myocardial infarction. Methods: This observational study involved 1994 suspected ST-elevation myocardial infarction patients presenting to the emergency medical services in Melbourne, Australia, between October 2011–January 2014. Factors associated with delays to emergency medical services call of >1 h and emergency medical services self-referral were analyzed using multivariable logistic regression. Results: The time of symptom onset was reported for 1819 patients (91.2%), the median symptom onset-to-call time was 52 min (interquartile range=17–176). Of all emergency medical services calls, 17% were referred by healthcare professionals. Compared to self-referred patients, patients who presented to a general practitioner or hospital had higher odds of delay >1 h to emergency medical services activation (adjusted odds ratio 7.76; 95% confidence interval 5.10–11.83; and 8.02; 3.65–17.64, respectively). The other factors associated with emergency medical services call delays of >1 h were living alone, non-English speaking background, a history of substance abuse, less severe symptoms, symptom onset at home and at rest, and self-treatment. Emergency medical services self-referred patients were more likely to be older than 75 years, have a history of ischemic heart disease or revascularization, more severe symptoms, and symptom onset at home, with activity, during the weekends and out-of-hours. Conclusion: Almost one-fifth of emergency medical services calls for suspected ST-elevation myocardial infarction were healthcare referrals, and this was associated with increased delays. A wide range of factors could influence a patient’s decision to directly and rapidly seek emergency medical services. More efforts are needed to educate at-risk populations about early self-referral to the emergency medical services.
The individual and neighborhood factors associated with the use of emergency medical services in patients with ST-elevation myocardial infarction