[Myocardial tissue vitality: clinical relevance, pathophysiology and identification]

Heart failure is an increasing clinical problem because of the rising frequency of admissions and the high mortality. Excellent long-term results are obtained with heart transplantation, whereas the long-term prognosis is poor when patients are treated medically. It has recently been demonstrated that, in patients with depressed left ventricular (LV) function, revascularization may be an alternative form of therapy, since improvement of LV function, which is an important prognostic factor, may occur after coronary revascularization. Recovery of LV function after revascularization may occur in patients with dysfunctional but viable myocardium, whereas no recovery can be expected in patients with scar tissue. Improvement of LV function after revascularization can be explained on the basis of the concept of myocardial tissue vitality': chronically ischaemic myocardium temporarily loses the facility to contract, but the contraction is regained after revascularization (once the ischaemia is eliminated). For the selection of patients who may profit by a revascularization procedure, techniques have been developed for the identification of dysfunctional but viable tissue. The myocardial glucose metabolism can be visualized by administration of 18F desoxyglucose (FDG) and imaging by positron emission tomography or 'single photon emission computer tomography'. Vital tissue shows diminished perfusion with intact glucose metabolism (FDG perfusion mismatch); a vital tissue shows diminished perfusion without glucose metabolism (FDG perfusion match). Scintigraphy of the membrane of the myocardial cell can also be investigated using 201Tl scintigraphy. Reserve contractility of the myocardium can be visualized by echocardiography during administration of dobutamine.