How to use information from echocardiography and magnetic resonance for diagnosing myocardial viability.

The identification of viable myocardium in patients with coronary artery disease with or without a history of myocardial infarction and regions of akinesia is of great clinical importance. Viable myocardium which is underperfused due to severe atherosclerotic disease in the feeding vessel needs to be revascularized both to ameliorate symptoms and improved prognosis. In contrast, scarred myocardium should not be revascularized and medical therapy for heart failure should be instituted. Due to the complexity of the problem, which requires information about wall motion and coronary artery anatomy, viability tests are usually requested after the results of left heart catheterization with coronary angiography are known. Often cardiac catheterization itself already provides important clues to the presence of viable myocardium: the degree of wall motion abnormality, post-extrasystolic improvement of wall motion, the presence of angina in a patient with single-vessel disease and the presence of collaterals, are all associated with viability. Echocardiography has become a strong competitor to myocardial perfusion studies in assessing myocardial viability. Published figures for sensitivity and specificity parallel those of scintigraphic techniques and even positron emission tomography scans. However, there are insufficient data on the use of echocardiography in patients with severely depressed left ventricular function. A new and exciting technique to detect viable myocardium is magnetic resonance imaging, which has been shown to have similar diagnostic accuracy as FDG-PET.