Unrecognised myocardial infarction in subjects at high vascular risk: prevalence and determinants

Objective: To investigate the prevalence and determinants of unrecognised myocardial infarction (UMI). Design, setting, patients: In this cross-sectional study in a tertiary centre, a delayed enhancement cardiac MRI (DE-CMR), which identifies both Q-wave and non-Q wave MIs, was performed in 502 subjects with manifest extracardiac atherosclerotic disease or marked risk factors for atherosclerosis without symptomatic coronary artery disease. Main outcome measures: UMI was defined as the presence of delayed enhancement without corresponding clinical history. Results: DE-CMR was of sufficient image quality in 480 (95.6%) subjects. A UMI was present in 45 (9.4%) of all subjects; in 13.1% of men and in 3.7% of women. The risk of UMI increased from 6.0% (95% CI 2.2 to 9.8%) in those with two vascular risk factors up to 26.2% (95% CI 15.2 to 37.3%) in those with four or five risk factors. In a multivariable analysis, the risk of UMI was related to male gender (OR 2.3 (95% CI 1.0 to 5.6)), age (OR 1.04 (95% CI 1.00 to 1.07) per year), ever smoking (OR 3.1 (95% CI 1.0 to 9.1), history of stroke (OR 1.9 (95% CI 0.8 to 4.3)) and history of aneurysm of the abdominal aorta (OR 2.6 (95% CI 1.0 to 6.9)). Conclusions: In cardiac asymptomatic subjects at high vascular risk, UMI is common. The risk of UMI increases with increasing presence of risk factors.