ASSESSMENT OF MYOCARDIAL VIABILITY BY USE OF C-11 ACETATE AND POSITRON EMISSION TOMOGRAPHY - THRESHOLD CRITERIA OF REVERSIBLE DYSFUNCTION

Background Dual positron emission tomography (PET) imaging with a perf usion tracer and F-18-fluorodeoxyglucose (FDG) can detect myocardial v iability. This approach may be replaced by a single C-11-acetate study , which enables quantification of both regional blood flow and oxidati ve metabolism. The significance of acetate-derived indexes for myocard ial viability is examined. Methods and Results Thirty postinfarct pati ents with akinetic ventricular segments, a mean ejection fraction of 4 2+/-11%, and high-grade coronary obstructions were studied with serial C-11-acetate PET scanning before and 7+/-5 months after coronary reva scularization. Acetate PET was tested against FDG and serial assessmen ts of segmental wall motion. Sixty of 155 severely dysfunctional LV se gments improved postoperatively, and regional blood flow increased. Fl ow estimates after revascularization suggested little fibrosis in reve rsible segments. At baseline, blood flows differed between normal myoc ardium, reversible dysfunction, and irreversible dysfunction (1.04+/-0 .27, 0.73+/-0.18, and 0.43+/-0.18 mL . min(-1). g(-1), respectively; P <.001). Oxidative metabolic rates were reduced only in irreversibly in jured LV segments. Multivariate analysis identified the acetate perfus ion index as the only independent predictor of postoperative recovery. Its predictive accuracy was similar to that of FDG imaging but superi or to indexes of flow-metabolic mismatch or oxidative metabolism. Conc lusions After myocardial infarction, quantitative indexes of perfusion and oxidative metabolism from acetate PET indicate a critical thresho ld beyond which tissue is irreversibly injured. Findings support the u se of blood how as a marker of myocardial viability in chronic postinf arct patients with modestly reduced ejection fractions.