1. Myocardial scars were detected by cardiac magnetic resonance (CMR) imaging in 7.9% of the study cohort, with the large majority undetected clinically or by electrocardiography (EKG).
2. Factors associated with presence of a myocardial scar include age, male sex, body mass index, hypertension and smoking.
Evidence Rating Level: 2 (Good)
Study Rundown: Cardiovascular disease poses a significant healthcare burden on the United States population. Prior studies have demonstrated that about 20% of myocardial infarctions (MIs) are clinically silent. Undetected MIs can result in myocardial scarring, which in turn can cause cardiac dysfunction. CMR imaging with late gadolinium enhancement can detect myocardial scars that are unrecognized clinically or by EKG.
This study used a U.S. population-based cohort, the Multi-Ethnic of Atherosclerosis (MESA) study, to determine the prevalence of myocardial scars using CMR and to determine the correlation of cardiovascular risk factors and coronary artery calcium (CAC) scores with the presence of a myocardial scar. It was found that 7.9% of the cohort had a CMR-detected myocardial scar, with 78% of scars being undetected clinically or by EKG. Older age, male sex, hypertension, higher BMI and current smoking were associated with higher odds of having a scar. Limitations of this study include the study population of the MESA cohort, which may make the study less generalizable to the population. Despite this, the results demonstrate a low prevalence of myocardial scar in this population. Further studies are needed to determine the significance of subclinical disease that results in myocardial scar.
In-Depth [retrospective cohort]: This population-based cohort study using the MESA study compared 1840 patients in 2000-2002 at baseline when they were free of cardiovascular disease to their CMR evaluation ten years later in 2010-2012. At 10 years, 7.9% (n=146) of the cohort had myocardial scars detected on CMR. Of these, 114 (78%) of the scars were unrecognized clinically or by EKG. The following cardiovascular disease risk factors were associated with higher odds of having a myocardial scar: older age (OR 1.61, 95% CI 1.36-1.91, p<0.001), male sex (OR 5.76, 95% CI 3.61-9.17, p<0.001), hypertension (OR 1.61, 95% CI 1.12-2.30), higher BMI (OR 1.32, CI 1.09-1.61, p=0.005) and current smoking (OR 2.00, 95% CI 1.22-3.28, p=0.006). In both cross-sectional and longitudinal analyses, the presence of a myocardial scar increased with CAC score. Thus this study demonstrates that both cardiovascular disease risk factors and CAC score are related to subclinical myocardial damage.
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