Pericardial effusion in primary hypothyroidism: Tc-99m sestamibi imaging

A 28-year-old woman was admitted to the hospital for an episode of syncope. On arrival, the patient was noticed to have an enlarged cardiac silhouette on chest x-ray. The ECG showed sinus bradycardia at 50 beats per minute. A resting myocardial perfusion study was performed after the injection of 20 mCi of Tc-99m sestamibi. The SPECT images show normal myocardial perfusion with a large pericardial effusion, best appreciated with planar images. Laboratory data showed a TSH of 284 mU/L, T₃ uptake 0.77, T₄ 0.4 mcg/dl, and a free thyroxine index less than 0.31. An echocardiogram showed a moderate to severe (600 cc) pericardial effusion with normal left ventricular function. Pericardial effusion may be a frequent manifestation in myxedema, an advanced severe stage.