Acute myocardial infarction in patients with syncope

Abstract

Objective: We sought to determine the incidence of acute myocardial infarction (AMI) in emergency department (ED) patients with syncope, the characteristics of these AMIs and how helpful the initial electrocardiogram (ECG) was in identifying these cases. Methods: In a prospective cohort of consecutive patients with syncope, the initial ECG was found to be abnormal using a prespecified definition (any nonsinus rhythm or any new or age-indeterminate abnormalities). Patients were then followed up to identify an AMI diagnosed within 30 days of presentation. Results: There were 1474 consecutive patient visits for syncope or near-syncope over a 45-month period spanning from Jul. 1, 2000, to Feb. 28, 2002, and Jul. 15, 2002, to Aug. 31, 2004, of which 46 (3.1%) were diagnosed with AMI. The majority of the AMI patients (42) had no ST segment elevation. The initial ECG was abnormal in 37 out of 46 cases. The diagnostic performance of the initial ECG was sensitivity 80% (95% confidence interval [CI] 67%-89%), specificity 64% (95% CI 61%-67%), negative predictive value 99% (95% CI 98%-100%), positive predictive value 7% (95% CI 6%-8%), positive likelihood ratio 2.2 (95% CI 1.6-2.5) and negative likelihood ratio 0.3 (95% CI 0.2-0.5). Conclusion: The incidence of AMI in patients presenting with syncope is low. A normal ECG has a high negative predictive value, although its sensitivity is limited.