MYOCARDIAL OXIDATIVE-METABOLISM IN HYPERTHYROID PATIENTS ASSESSED BY PET WITH CARBON-11-ACETATE

Hyperthyroid patients often complain of cardiovascular symptoms becaus e of increased metabolism. This study was designed to quantitatively e valuate myocardial oxidative metabolism in these patients. Methods: Dy namic PET with C-11-acetate was performed in 19 patients who had not u ndergone treatment for hyperthyroidism. Eight were restudied 2 wk afte r oral administration of propranolol. The clearance rate constant of C -11-acetate (Kmono) was calculated with monoexponential fitting of tra cer washout from the myocardium as a marker of myocardial oxidative me tabolism. The results were compared with those in nine normal subjects both at rest and during dobutamine infusion. Results: Kmono in our pa tients (0.109 +/- 0.028 min(-1)) was significantly increased compared to normal subjects (0.066 +/- 0.016 min(-1)) (p < 0.05). After propran olol treatment, Kmono decreased (0.082 +/- 0.014 min(-1)) but remained significantly higher in eight patients than normal subject levels (p < 0.05), while the rate pressure product decreased significantly (7500 +/- 1700) toward the normal range (7900 +/- 1500). Conclusion: These results suggest the possibility of excessive myocardial oxygen consump tion in hyperthyroid patients. The clearance rate of C-11-acetate is a new and valuable index to assess myocardial oxidative metabolism not closely related to the pressure rate product or thyroid hormones in th ese patients.