New concepts in characterization of ischemically injured myocardium by MRI

New concepts regarding the assessment of ischemic myocardial injuries have been addressed in this Minireview using magnetic resonance imaging (MRI). M RI, with its different techniques, brings not only anatomic, but also physi ologic, information on ischemic heart disease. It has the ability to measur e identical parameters in preclinical and clinical studies. MRI techniques provide the ideal package for repeated and noninvasive assessment of myocar dial anatomy, viability, perfusion, and function. MR contrast agents can be applied in a variety of ways to improve MRI sensitivity for detecting and assessing ischemically injured myocardium. With MR contrast agents protocol , it becomes possible to identify ischemic, acutely infarcted, and peri-inf arcted myocardium in occlusive and reperfused infarctions. Necrosis specifi c and nonspecific extracellular contrast-enhanced MRI has been used to asse ss myocardial viability. Contrast-enhanced perfusion MRI can explore the di sturbances in large (angiography) and small coronary arteries (myocardial p erfusion) as the underlying cause of myocardial dysfunction, Perfusion MRI has been used to measure myocardial perfusion (ml/min/g) and to demonstrate the difference in transmural myocardial blood flow. Information on no-refl ow phenomenon is derived from dynamic changes in regional signal intensity after bolus injection of MR contrast agents. Another development is the nea r future availability of blood pool MR contrast agents. These agents are ab le to assess microvascular permeability and integrity and are advantageous in MR angiography (MRA) due to their persistence in the blood. Noncontrast- enhanced MRI such as cine MRI at rest/stress, sodium MRI, and MR spectrosco py also have the potential to noninvasively assess myocardial viability in patients. Futuristic applications for MRI in the heart will focus on identi fying coronary artery disease at an early stage and the beneficial effects of new therapeutic agents such as intra-arterial gene therapy. MR technique s will have great future in the drug discovery process and in testing the e ffects of drugs on myocardial biochemistry, physiology, and morphology. Mol ecular imaging is going to bloom in this decade.