(HealthDay News) – For older patients, the prevalence of unrecognized myocardial infarction (UMI), as assessed by cardiac magnetic resonance (CMR) imaging, is higher than that of recognized myocardial infarction (RMI) and correlates with increased mortality, according to a study published in the Sept 5 issue of the Journal of the American Medical Association.

Erik B Schelbert, MD, from the National Institutes of Health in Bethesda, MD, and colleagues conducted a cohort substudy involving 936 older adults from the Age, Gene/Environment Susceptibility-Reykjavik Study, aged 67–93 years, including 670 who were randomly selected and 266 with diabetes.

The researchers found that 9.7% of participants had RMI. Seventeen percent of participants had UMI detected by CMR, which was significantly more prevalent than the 5% detected by electrocardiography (ECG). More UMI was detected by CMR than ECG among participants with diabetes (21% vs. 4%). Atherosclerosis risk factors, coronary calcium, coronary revascularization, and peripheral vascular disease were associated with UMI detected by CMR. Over a median of 6.4 years of follow-up, 33% of participants with RMI died and 28% with UMI died, compared with 17% with no MI who died. Risk stratification for mortality was improved for UMI by CMR beyond RMI (net reclassification improvement, 0.34). UMI by CMR remained significantly associated with increased risk of mortality, after adjustment for age, sex, diabetes, and RMI (hazard ratio, 1.45), and significantly improved risk stratification for mortality (net reclassification index, 0.16). UMI by ECG was not linked to increased risk of mortality.

“In a community-based cohort of older individuals, the prevalence of UMI by CMR was higher than the prevalence of RMI and was associated with increased mortality risk,” the authors write.

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