Clinically Unrecognized Myocardial Scars Detected by MRI
Abstract: A high percentage of unrecognized myocardial infarctions (UMIs) seen at delayed-enhanced magnetic resonance imaging (DE-MRI) are not detected by ECG. DE-MRI-detected UMIs are independent predictors of cardiovascular events in patients with coronary artery disease. In an elderly population, subjects with DE-MRI-detected UMIs do not have increased Framingham risk score or increased prevalence of artery stenosis in whole-body MR angiography as patients with recognized myocardial infarctions (RMI). Further investigation on the pathogenesis of DE-MRI-detected UMIs focus on the need to decide the management of these subjects.From the Prospective Investigation of the Vasculature in Uppsala Seniors, 248 subjects underwent cardiac MRI at age 70 and from these, 185 underwent a 5-year follow-up MR. DE-MRI-detected UMIs had lower signal intensity than RMIs probably reflecting different composition of their tissues. Subjects with UMI scar had increased levels of NT-proBNP, a predictor of increased risk of cardiovascular events. After 5 years, UMI scars were in their majority seen on the same location and with the same size, and their prevalence increased. Subjects with an UMI did not differ from subjects without a scar in terms of coronary stenosis assessed by computed tomography angiography or signs of ischemia on exercise test.In conclusion, DE-MRI-detected UMI scars are a frequent finding in an elderly population and its prevalence increases with age. The increased levels of NT-proBNP indicate that subjects with an UMI might have an increased rate of future cardiovascular events but the findings that these scars might have a different contrast distribution volume on MRI and that they are not related to CAD are indicators that they probably have a different etiology from RMIs. The prognosis of DE-MRI detected UMI scars in the general population is still unknown and therefore the clinical management of these individuals is yet to be defined.
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