JAMA: Cardiac MR reveals higher rate of unrecognized heart attacks

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In a study of older adults, cardiac MR (CMR) imaging was able to detect more unrecognized heart attacks and was more strongly associated with mortality than electrocardiography (ECG), according to results published in the Sept. 5 issue of the Journal of the American Medical Association.

"The prevalence and prognosis of unrecognized myocardial infarction (MI) in older people with and without diabetes may be higher than previously suspected in population studies,” wrote authors Erik B. Schelbert, MD, MS, of the National Institutes of Health in Bethesda, Md., and colleagues. “Advances in MI detection, such as [CMR] imaging with late gadolinium enhancement (LGE), are more sensitive than prior methods.”

Schelbert and colleagues sought to compare the prevalence and prognosis of recognized and unrecognized MI (RMI and UMI) diagnosed with CMR vs. ECG in older diabetic and nondiabetic participants from a community-dwelling group in Iceland. The study, dubbed ICELAND MI, is a cohort substudy of the Age, Gene/Environment Susceptibility-Reykjavik Study, which used ECG or CMR to detect UMI.

Data for 936 participants, enrolled from January 2004 to January 2007, were included in the study. Participants were between the ages of 67 and 93 years, with a median age of 76. Of the larger group, 670 were randomly selected, while 266 were selected for having diabetes.

A total of 91 participants (9.7 percent) had RMI and prevalence of UMI by CMR was 17 percent. Those with diabetes had a higher prevalence of UMI by CMR than those without diabetes, with rates of 21 percent and 14 percent, respectively. Only 46 UMI were detected by ECG, for a prevalence of 5 percent. UMI by CMR was associated with atherosclerosis risk factors, coronary calcium, coronary revascularization and peripheral vascular disease, according to the authors.

Over a median follow-up of 6.4 years, 33 percent of the participants with RMI died, as did 28 percent of those with UMI by CMR. Both rates were significantly higher than the 17 percent with no MI who died, according to Schelbert et al. After adjusting for age, sex, diabetes and RMI, UMI by CMR remained associated with mortality, but UMI by ECG was not.

Participants with UMI by CMR used more aspirin, beta-blocker and statin medications than those without MI, noted the authors, but use of these medications was less in those with UMI compared with those with RMI. “Roughly half of those with UMI were taking aspirin, whereas less than half were taking statins or beta-blockers."

Schelbert and colleagues wrote that the results suggest limitations in current prevention strategies. “The burden of UMI was higher than the total burden of recognized MI, and prescription of cardioprotective medications was less than for participants with RMI. The high prevalence of MI specifically in individuals with diabetes confirms their increased vulnerability. Less than one-third of those with UMI by CMR had prior revascularization to establish coronary disease and trigger secondary prevention strategies. Detection of UMI by CMR may provide an opportunity to optimize treatment for these vulnerable individuals, but further study is needed to assess this."