Myocardial Scars Go Undetected in Many Older Patients

Diana Phillips

November 11, 2015

Many older Americans have heart attacks that go unnoticed, according to the findings of a large, population-based study. Nearly 8% of a multiethnic cohort of men and women (mean age, 68 years) who were free of clinical cardiovascular disease at the beginning of the study had documented myocardial scars on cardiac magnetic resonance imaging at year 10.

Of the individuals with evidence of scarring, 78% were unrecognized by electrocardiography or clinical evaluation, Evrim B. Turkbey, MD, from the National Institutes of Health Clinical Center, National Institute of Biomedical Imaging and Bioengineering, Bethesda, Maryland, and colleagues report in the November 10 issue of JAMA.

Given the aging of the US population, understanding the prevalence, risk factors, and prognosis of these silent myocardial infarctions is increasingly important, the authors write.

To determine the prevalence of myocardial scars and to evaluate the association between cardiovascular disease risk factors and myocardial scar, the authors analyzed data from the Multi-Ethnic Study of Atherosclerosis, which enrolled multiethnic participants aged from 45 through 84 years and free of cardiovascular disease at study entry in 2000 to 2002. In study year 10, 1840 participants underwent cardiac magnetic resonance imaging with gadolinium to detect myocardial scarring. The researchers measured cardiovascular disease risk factors and coronary artery calcification (CAC) scores at baseline and year 10.

Overall, 78% (114 of 146) of myocardial scars were unrecognized by clinical exam or electrocardiography; of those, 38% (43 of 114) were typical and 62% (71 of 114) were atypical scars. Among recognized myocardial scars, 84% (27 of 32) were typical, and 16% (5 of 32) were atypical. The prevalence of myocardial scar was significantly higher in men, at 12.9%, than in women, at 2.5% (difference, 10.4%; 95% confidence interval, 8% - 13%; P < .001).

After adjusting for age and sex, logistic regression models showed that age, male sex, body mass index, hypertension, and current smoking at baseline were associated with myocardial scar at year 10. In addition, age-, sex-, and ethnicity-adjusted CAC scores at baseline were also associated with a myocardial scar at year 10, the authors report.

"The prevalence of myocardial scar increased in relationship to CAC score: 3.5% for scores of 0, 10.6% for scores ranging from 1 through 99, 11.4% for scores ranging from 100 through 399, and 16.7% for scores of 400 or higher, as did the corresponding [odds ratios] adjusted for age, sex, and race/ethnicity," the authors write.

The association between the CAC score and subclinical myocardial damage may have important clinical relevance. "The CAC score is an important measure of subclinical atherosclerotic burden and is an independent predictor of coronary heart disease and cardiovascular disease," the authors explain.

Although Framingham and American College of Cardiology/American Heart Association risk scores were also associated with myocardial scar in this cohort, other established risk factors including serum lipid levels and diabetes showed no significant association with myocardial scar. Confounding introduced by concurrent medication use may explain this finding, the authors hypothesize.

An assessment of myocardial scar risk by ethnicity showed that Chinese and Hispanic ethnicity had lower odds of myocardial scar than European or African ethnicity.

Although the clinical significance of unrecognized myocardial scar is unknown, "prior myocardial scar has been noted pathologically in more than 70% of patients with sudden cardiac death but without prior known coronary artery disease," the authors explain.

Because ischemic heart disease is an important public health concern, "Further studies are needed to understand the clinical consequences of these undetected scars," the authors conclude.

The authors have disclosed no relevant financial relationships.

JAMA. 2015;314:1945-1954. Abstract

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