Initial risk stratification and presenting characteristics of patients with evolving myocardial infarctions

Objectives: To describe the presenting characteristics and risk stratification of patients presenting to the emergency department with chest pain who have a normal initial troponin level followed by a raised troponin level within 12 h (evolving myocardial infarction (EMI)). Methods: Data from the Internet Tracking Registry for Acute Coronary Syndromes (i*trACS), a registry of patients presenting with undifferentiated chest pain, were used. This analysis included patients without ST segment elevation with at least two troponin assay results <= 12 h apart. Patients were stratified into three groups: EMI (initial troponin assay negative, second troponin assay positive), non-ST elevation myocardial infarction (NSTEMI) (initial troponin assay positive) and no MI (all troponin assays negative). Results: Of 4136 eligible patients, 5% had EMI, 8% had NSTEMI and 87% had no MI. Patients with EMI were more similar to those with NSTEMI than those with no MI with respect to demographic characteristics, presentation, admission patterns and revascularisation. The initial ECG in patients with EMI was most commonly nondiagnostic (51%), but physicians' initial impressions commonly reflected MI, unstable angina or high-risk chest pain (76%). This risk assessment was followed by a high rate of critical care admissions (32%) and revascularisation (percutaneous coronary intervention 17%) among patients with EMI. Conclusion: Patients with EMI appear similar at presentation to those with NSTEMI. Patients with EMI are perceived as being at high risk, evidenced by similar diagnostic impressions, admission practices and revascularisation rates to patients with NSTEMI.