Myocardial oxidative metabolism in hyperthyroid patients assessed by PET with carbon-11-acetate.
Hyperthyroid patients often complain of cardiovascular symptoms because of increased metabolism. This study was designed to quantitatively evaluate myocardial oxidative metabolism in these patients.


METHODS
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.


RESULTS
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).


CONCLUSIONS
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.
D000085:Acetates; D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D000328:Adult; D002250:Carbon Radioisotopes; D016022:Case-Control Studies; D005260:Female; D006111:Graves Disease / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000378:metabolism*; D006321:Heart / Q000000981:diagnostic imaging*; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D011433:Propranolol / Q000627:therapeutic use; D013963:Thyroid Hormones / Q000097:blood; D014055:Tomography, Emission-Computed
D000085:Acetates; D000319:Adrenergic beta-Antagonists; D002250:Carbon Radioisotopes; D013963:Thyroid Hormones; D011433:Propranolol