Myocardial Scars More Frequent Than Expected

OBJECTIVES: The aim of this study was to investigate the prevalence of clinically recognized myocardial infarctions (RMIs) and unrecognized myocardial infarctions (UMIs) in 70-year-old subjects, assessed with magnetic resonance imaging (MRI), and to relate the findings to cardiac function and morbidity. BACKGROUND: Late enhancement MRI identifies myocardial scars and thereby has the potential to detect UMI. METHODS: Cardiac MRI was performed on 259 randomly chosen 70-year-old subjects. Late enhancement and cine sequences were acquired, and the ejection fraction and left ventricular (LV) mass were calculated. Late enhancement involving the subendocardial layer was considered to represent myocardial infarction (MI) scars, and their volumes were calculated. Information on cardiac morbidity and risk factors was collected from medical records and from a health examination. Subjects with MI scars, with or without a hospital diagnosis of MI were classified as RMI or UMI, respectively. RESULTS: The images from 248 subjects (123 women, 125 men) were assessable. Myocardial infarction scars were found in 60 subjects (24.2%), in 49 of whom (19.8%) they were UMIs. The volumes of the UMIs were significantly smaller than those of the RMIs. There was an increased frequency of chest pain symptoms among the subjects with UMI or RMI compared with those without MI scars. Ejection fraction was significantly lower and LV mass significantly larger in the subjects with UMI or RMI than in those without MI scars. CONCLUSIONS: Unrecognized MI detected with MRI was more frequent than expected in 70-year-old subjects. The subjects displaying these UMIs may represent a previously unknown potential risk group for future cardiovascular events.