This project is intended to improve methods to detect a heart blood clot or “thrombus,” and a heart valve problem called mitral valve regurgitation, for people who are recovering from a heart attack. Another goal is to find ways to predict the risks that these conditions may pose for these patients. The traditional way to detect thrombus and mitral valve regurgitation is by means of echocardiography. This study compares echocardiography to MRI, in the hope that the imaging power of MRI will improve physicians’ ability to identify patients’ potential risks, and thereby help in their treatment. Funding is provided by the National Institutes of Health under grant K23 HL102249 with principal investigator Jonathan Weinsaft, MD. Some elements of the study are also funded by a clinical research grant from the Lantheus Corporation. This study is currently open to enrollment: see studies open to enrollment.