Case report: reversible mitral regurgitation and congestive heart failure complicating thyrotoxicosis.

Congestive heart failure is a relatively uncommon manifestation of thyrotoxic heart disease, and different mechanisms have been proposed. The authors present a possible explanation of congestive heart failure in some cases of thyrotoxicosis. A 39 year-old woman with Graves' disease was hypermetabolic, in atrial fibrillation, and had signs of congestive heart failure. She had a loud murmur of mitral regurgitation, clinical cardiomegaly, accentuated pulmonic sound, and peripheral edema. Propranolol reduced the heart rate to 60 beats per minute, but the loud mitral regurgitation murmur persisted. Echocardiographic and angiographic data were consistent with moderate to severe mitral regurgitation, serious enough to consider mitral valve replacement. As the patient's hyperthyroid state came under control, weight increased and the cardiac murmur resolved. After radioactive iodine treatment and the return to a eumetabolic state, an echocardiogram revealed only trace mitral regurgitation, with near normal left ventricular function and pulmonary arterial systolic pressures. These findings were confirmed by subsequent cardiac catheterization. The authors believe that mitral regurgitation, perhaps secondary to intrinsic papillary muscle dysfunction from hyperthyroidism, was the major cause of reversible congestive heart failure in this case. Valvular disease may play a more substantive role in thyrotoxic heart disease than previously recognized.