ASSESSMENT OF MYOCARDIAL VIABILITY BY DOBUTAMINE ECHOCARDIOGRAPHY, POSITRON-EMISSION-TOMOGRAPHY AND TL-201 SPECT - CORRELATION WITH HISTOPATHOLOGY IN EXPLANTED HEARTS

Objectives. We examined the relationship among viability assessment by dobutamine echocardiography (DE), positron emission tomography (PET) and thallium-201 single-photon emission computed tomography (TI-SPECT) to the degree of fibrosis. Background. DE, PET and TI-SPECT have been shown to be sensitive in identifying viability of asynergic myocardiu m. However, PET and TI-SPECT indicated viability in a significant perc entage of segments without dobutamine response or functional improveme nt after revascularization. Methods. Twelve patients with coronary art ery disease and severely reduced left ventricular function (EF 14.5 +/ - 5.2%) were studied with DE prior to cardiac transplantation: 5 had a dditional PET and 7 had Tl-SPECT studies. Results of the three techniq ues were compared to histologic findings of the explanted hearts. Resu lts. Segments with >75% viable myocytes by histology were determined t o be viable in 78%, 89% and 87% by DE, PET and Tl-SPECT; those with 50 -75% viable myocytes in 71%, 50% and 87%, respectively. Segments with 25-50% viable myocytes showed response to dobutamine in only 15%, but were viable in 60% by PET and 82% by Tl-SPECT. Segments with <25% viab le myocytes responded to dobutamine in 19%; however, PET and TI-SPECT demonstrated viability in 33% and 38%, respectively. Discrepant segmen ts without dobutamine response but viability by PET and SPECT had sign ificantly more viable myocytes by pathology than did those classified in agreement to be nonviable but had significantly less viable myocyte s than those classified in agreement to be viable (p < .001). Conclusi ons. These findings suggest that contractile reserve as evidenced by a positive dobutrtmine response requires at least 50% viable myocytes i n a given segment whereas scintigraphic methods also identify segments with less viable myocytes. Thus, the methods may provide complementar y information: Nuclear techniques appear to be highly sensitive for th e detection of myocardial viability, and negative tests make it highly unlikely that a significant number of viable myocytes are present in a given segment. Conversely, dobutamine echo may be particularly usefu l for predicting recovery of systolic function after revascularization . (J Am Cell Cardiol 1998;32:1701-8) (C) 1998 by the American College of Cardiology.