Do risk factors for chronic coronary heart disease help diagnose acute myocardial infarction in the Emergency Department?

BACKGROUND: Hypertension, hyperlipidaemia, diabetes mellitus, tobacco smoking and a family history of premature coronary artery disease are known to be risk factors for the development of coronary artery disease. We sought to determine whether these traditional risk factors aid the diagnosis of acute myocardial infarction (AMI) in the Emergency Department (ED).

METHODS: We performed a prospective diagnostic cohort study within the ED at Manchester Royal Infirmary, a university-affiliated teaching hospital with an annual ED census of approximately 145,000 patients. We recruited 804 patients who had presented to the ED with suspected cardiac chest pain. All patients had the presence or absence of traditional cardiac risk factors documented at the time of presentation using a custom-designed clinical report form. All patients subsequently underwent 12-h troponin T testing to provide a robust gold standard for the diagnosis of AMI according to revised World Health Organisation criteria.

RESULTS: The absence of any traditional cardiac risk factors carried a negative likelihood ratio of 0.61 for the diagnosis of AMI. 12.2% of patients with no cardiac risk factors had AMI, compared with 21.3% of patients with four or five risk factors. The area under the receiver-operating characteristic curve was 0.49.

CONCLUSIONS: Traditional cardiac risk factors are not helpful for the confirmation or exclusion of AMI within the ED. Future Emergency Medicine research should focus on those clinical and diagnostic features that are likely to alter during the acute phase of illness.