Scintigraphic evaluation of the ischemically damaged myocardium in patients with reduced left ventricular function. From clinical aspects to the cell

: Identification of viable myocardium in patients with impaired left ventricular function, who are possible candidates for revascularization, represents an important clinical question. Modern methods of revascularization provide a therapeutic alternative to conventional pharmacological therapy even in patients with advanced ischemic heart disease. Modern diagnostic techniques make it possible to assess not only the extent of ischemia under exercise conditions, but also the presence of viable tissue in patients with severe coronary artery disease and impaired ventricular function. Currently, the most accurate methods for scintigraphic quantification of viable myocardial tissue are metabolic investigations with positron emission tomography (PET). Because of the limited availability of PET other methods like thallium-201-scintigraphy play an important clinical role. Modifications of thallium-201-scintigraphy, for example the introduction of reinjection protocols have improved the recognition of viable tissue and decreased the diagnostic difference to PET. We recommend as standard diagnostic procedure for assessment of tissue viability thallium-201-scintigraphy with reinjection. In patients with severely depressed left ventricular function and equivocal thallium-201-scintigraphy findings, PET should be considered as further diagnostic test. Low dose dobutamine-echocardiography is emerging as alternative test for evaluation of contractile reserve in dysfunctioning left ventricular segments. Its clinical role, however, remains to be determined. Besides the clinical application of these methods, newly developed radiotracers, together with PET, may provide insights into the mechanism of metabolic adaptations in patients with repeated episodes of ischemia. Furthermore, correlation of clinical data with in vitro histological and biological tissue analysis in the same patients may provide a better understanding of metabolic alterations observed in chronic ischemic heart disease.