Body surface mapping versus the standard 12 lead ECG in the detection of myocardial infarction amongst Emergency Department patients: a Bayesian approach

Abstract

Objective: To determine if body surface mapping (BSM) is better than the standard 12 lead ECG in the diagnosis of acute myocardial infarction amongst emergency department patients. Setting: A University affiliated inner-city emergency department. Participants: People presenting to an emergency department with symptoms compatible with myocardial ischaemia/infarction. Main outcome measures: Myocardial infarction as defined by either standard 12 lead ECG changes with associated cardiac marker rise, Troponin T >0.1 μg/ml at >12 h or autopsy/surgical findings of fresh macroscopic infarction. Results: BSM had an overall sensitivity of 47.1% versus 40% for the 12 lead ECG ( P < 0.001). Specificity for the BSM was 85.6% versus 93.7% for the 12 lead ECG ( P < 0.001). These findings were consistent for low/moderate and high risk subgroups. Bayesian analysis demonstrates that indiscriminate use of BSM would result in a clinically important overdiagnosis of myocardial infarction amongst emergency department patients. Conclusions: BSM has a higher sensitivity, but a lower specificity for the diagnosis of myocardial infarction.