Torizuka T, Tamaki N, Kasagi K, Misaki T, Kawamoto M, Tadamura E, Magata Y, Yonekura Y, Mori T, Konishi J
Department of Nuclear Medicine, Kyoto University Faculty of Medicine, Japan.
J Nucl Med. 1995 Nov;36(11):1981-6.
Hyperthyroid patients often complain of cardiovascular symptoms because of increased metabolism. This study was designed to quantitatively evaluate myocardial oxidative metabolism in these patients.
Dynamic PET with 11C-acetate was performed in 19 patients who had not undergone treatment for hyperthyroidism. Eight were restudied 2 wk after oral administration of propranolol. The clearance rate constant of 11C-acetate (Kmono) was calculated with monoexponential fitting of tracer washout from the myocardium as a marker of myocardial oxidative metabolism. The results were compared with those in nine normal subjects both at rest and during dobutamine infusion.
Kmono in our patients (0.109 +/- 0.028 min-1) was significantly increased compared to normal subjects (0.066 +/- 0.016 min-1) (p < 0.05). After propranolol 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).
These results suggest the possibility of excessive myocardial oxygen consumption in hyperthyroid patients. The clearance rate of 11C-acetate is a new and valuable index to assess myocardial oxidative metabolism not closely related to the pressure rate product or thyroid hormones in these patients.
