Characteristics and occurrence of type 2 myocardial infarction in emergency department patients: a prospective study

Objective To identify differences in prevalence, demographics, clinical features and outcomes for type 1 myocardial infarction (T1MI) and type 2 myocardial infarction (T2MI) in a cohort of patients presenting to the Emergency Department (ED) with chest pain. Methods This was a post hoc analysis of data collected from two prospective studies. Data were collected between November 2008 and February 2011 for the first study, and between February 2011 and March 2014 for the second. Participants were patients presenting to the ED with symptoms suggestive of acute coronary syndrome (ACS). The outcome was 30-day diagnosis; classified into T1MI, T2MI or non-MI. Descriptive statistics were used to compare the demographics, clinical history and presenting symptoms across diagnoses (T1MI, T2MI and non-MI). Cumulative mortality over 1 year was compared for T1MI and T2MI. Results 147 patients (6.3%; 95% CI 5.3% to 7.3%) were classified as T1MI and 52 (2.2%; 95% CI 1.7% to 2.9%) were classified as T2MI. T2MIs were more likely to be female (OR 4.71, 95% CI 2.28 to 9.76), have an abnormal but non-ischaemic ECG (OR 2.95, 95% CI 1.45 to 6.00), report prior hypertension (OR 2.83, 95% CI 1.35 to 6.12), have tachycardia (OR 9.26, 95% CI 3.08 to 30.77) and pain at rest (OR 3.04, 95% CI 1.28 to 8.02) compared with T1MI. One-year mortality was similar between T1MI and T2MI (9% and 14.6%, respectively, p=0.37). Conclusions T2MIs comprised one quarter of all MIs diagnosed in the ED. Among patients presenting to the ED with symptoms of ACS, symptoms do not allow clinicians to reliably differentiate patients with T1MI and T2MI. Prior hypertension, tachycardia and abnormal non-ischaemic ECGs are seen more often in T2MI compared with T1MI. One- year mortality was substantial in patients with T1MI and T2MI, but low power precludes conclusions about mortality differences between groups.