Characteristics of prehospital ST-segment elevation myocardial infarctions

Despite attention directed at treatment times of ST-segment elevation myocardial infarctions (STEMIs), little is known about the types of STEMIs presenting to the emergency department (ED).

The purpose of this study was to determine the relative frequencies and characteristics of emergency medical services (EMS) STEMIs compared with those in patients who present to the ED by walk-in. This information may be applied in EMS training, system planning, and public education.

This was a query of a prospectively gathered database of all STEMIs in patients presenting to Summa Akron City Hospital ED in 2009 and 2010. We collected demographic information, chief complaint, mode and time of arrival, and STEMI pattern (anterior, lateral, inferior, or posterior). We excluded transfers and in-hospital STEMIs. We calculated means, percentages, significance, and 95% confidence intervals (CIs) ± 10%.

We analyzed data from 308 patients. Most patients (241/308, 78%, CI 73%-83%) arrived by EMS, were male (203/308, 66%, CI 60%-71%), and were white (286/308, 93%, CI 89%-96%). Patients arriving by EMS were older (average 63 years, range 35-95) than walk-in patients (average 57 years, range 24-92). Two percent (5/241, 2%, CI 1%-5%) of EMS STEMI patients were under 40 years of age, compared with 10% (7/67, 10%, CI 4%-20%) of walk-in patients (p = 0.0017). The most common chief complaint was chest pain (278/308, 90%, CI 86%-93%). Inferior STEMIs were most common (167/308, 54%, CI 49%-60%), followed by anterior (127/308, 41%, CI 48%-60%), lateral (8/308, 3%, CI 1%-5%), and posterior (6/308, 2%, CI 1%-4%). A day-of-the-week analysis showed that no specific day was most common for STEMI presentation. Forty percent (122/308, 40%, CI 34%-45%) of patients presented during open catheterization laboratory hours (Monday through Friday, 0730-1700 hours). There was no significant statistical difference between EMS and walk-in patients with regard to STEMI pattern or patient demographics.

In this study, 95% (294/308) of all STEMIs were inferior or anterior infarctions, and these types of presentations should be stressed in EMS education. Most STEMI patients at this institution arrived by ambulance and during off-hours. Younger patients were more likely to walk in. We need further study, but we may have identified a target population for future interventions. Key words: emergency medical services; allied health personnel; electrocardiography; myocardial infarction; heart catheterization; STEMI.