Massera D, et al. - Using cardiac magnetic resonance imaging (MRI), researchers assessed the prevalence of unexplained left ventricular (LV) hypertrophy in 4972 individuals in MESA (Multi-Ethnic Study of Atherosclerosis). Participants were free of overt cardiovascular disease, aged 45 to 84 years, and had undergone measurement of regional LV wall thickness by cardiac MRI as part of the MESA baseline exam. The following subjects were excluded: individuals with hypertension, LV dilation (≥95% predicted end-diastolic volume) or dysfunction (ejection fraction ≤50%), moderate-to-severe left-sided valve lesions by cardiac MRI, severe aortic valve calcification by cardiac computed tomography (aortic valve Agatston calcium score >1200 in women or >2000 in men), obesity (body mass index >35 kg/m²), diabetes mellitus, and current smoking. In this population-based cohort, the prevalence of unexplained LV hypertrophy by cardiac MRI was 1.4%. Across categories of race/ethnicity, similar prevalence was found.