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Gated SPECT Findings Revealing Diastolic Dysfunction in Acute Hypothyroidism

Purpose: The purpose of this study was to assess left ventricular (LV) function by gated SPECT in acute hypothyroidism. Methods: Thirty-eight acute hypothyroid patients without any cardiac disease and 40 healthy controls underwent gated SPECT at rest. Fourteen patients had a second examination during thyroxine replacement therapy. Gated SPECT was performed using Tc-99m sestamibi with 16 frames per cardiac cycle. The LV end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), peak ejection rate (PER), peak filling rate (PFR), and time to peak filling (TTPF) were measured by quantitative gated SPECT (QGS). Systolic wall thickening/motion was determined in 5 myocardial segments. Results: Hypothyroid patients exhibited a decrease in PFR (222 ± 52 EDV/s) and prolongation of TTPF (194 ± 32 msec) as compared with controls (247 ± 41 EDV/s and 179 ± 17 msec, respectively; P < 0.05). During thyroxine therapy, the mean values for EDV (74 ± 21 mL) and PFR (265 ± 64 EDV/s) increased significantly in 14 follow-up patients (pretreatment values 67 ± 18 mL and 219 ± 50 EDV/s, respectively; P < 0.05). A significant difference was detected in the mean TTPF between the thyroxine group and the controls (195 ± 35 msec vs 179 ± 17 msec; P < 0.05). No significant differences were found in wall thickening and motion values (P > 0.05). Conclusion: Gated SPECT findings revealed diastolic dysfunction as indicated by a decrease in PFR and a prolongation in TTPF in patients with acute hypothyroidism.