PET Imaging of Oxidative Metabolism Abnormalities in Sympathetically

This study was designed to test the hypothesis that regional sympathetic denervation produces perfusion and metabolic alter ations in myocardial tissue under resting conditions. Methods: PET studies of myocardial sympathetic innervation, myocardial perfusion and oxygen utilization using ["CJhydroxyephedrine (HED), [13N]ammonia and 1-[11C]acetate, respectively, were per formed before and approximately 2 and 8 wk after surgical left thoracotomy and regional chemical sympathetic denervation (n = 5). A second group of animals underwent the same surgical procedure but, so that they could serve as a sham control group, were not sympathetically denervated (n = 5). The second group of animals was imaged before and 2 wk after surgery. Images of the retention of [1'C]HED taken from 50 to 60 min postinjection were used to differentiate sympathetically innervated and dener vated regions of the left ventricle. Regions of interest were defined on polar plots of the [11C]HED retention, including the sympathetically denervated territory and normally innervated regions. Regions defined on the HED polar plots were then transferred to the [13N]ammonia and 1-[11C]acetate image data, and tracer kinetic models were fit to the regional time-activity curves to generate estimates of myocardial perfusion and oxida-tive metabolism. Results: The average percentage of the left ventricle denervated in the group I animals was 13.1 % ±7.3%. Significant reductions in oxidative metabolism were observed in the sympathectomized tissue both at 2 and 8 wk after surgery (22 % and 15 % reductions, respectively). Significant alterations in regional perfusion were not observed. No significant changes in oxidative metabolism or perfusion were observed in the sham control group. Conclusion: Regional sympathetic denervation alters oxidative metabolism but not perfusion in the denervated region of the heart. Key Words: PET; myocardialoxidative metabolism;myocardial blood flow; autonomie nervous system; sympathetic denervatio