Following a myocardial ischemic event, a number of changes take place in the affected part of the myocardium. The center of the ischemic region may be irreversibly damaged, leading to cell death and necrosis. Surrounding this central infarct zone is a region at risk, where the myocardium has been affected by the ischemic event but, with proper intervention, still has the potential for recovery. Information about the extent of the viable region is essential for diagnosis, prognosis, and the planning of appropriate intervention. The applicants proposed to differentiate irreversibly damaged (IR), ischemically insulted but viable (IV), and hibernating (H) myocardium from normal tissue non-involved and without contrast agents using nuclear magnetic resonance (NMR) imaging and spectroscopic techniques. These techniques include: function cine imaging to identify the contractile properties of the myocardium; magnetization transfer contrast imaging to identify IR tissue; T2-weighted turbo spin echo imaging to identify IR and IV tissue; and water-suppressed lipid imaging and 1H spectroscopic imaging to identify IV. Hibernating myocardium is identified by lipid imaging in conjunction with abnormal contraction. Patients who have had recent infarcts or have chronic stable ischemic disease or have ischemic cardiomyopathies have varying degrees of IR, IV, and H. By studying these patients and following up where appropriate, the applicants proposed to confirm the identification of these different tissues. In addition, the MTC effect is little understood in the heart. Using a canine model of ischemia, the applicants proposed to follow the development of the MTC effect and compare it to both ex vivo. images and histology. By using these approaches together with the high quality functional images that can be generated by proton nuclear magnetic resonance cardiac imaging, the type and extent of ischemic damage should be assessable. Once accomplished successfully, such information derived clinically could have an impact on the future of the practice of cardiology.
