Reversible dilated cardiomyopathy due to subclinical hyperthyroidism.

We present a patient without primary heart disease in whom subclinical hyperthyroidism was accompanied by manifestations of dilated cardiomyopathy, as evaluated by echocardiography, coronary angiography, and radionuclide ventriculography. His condition was reversed 6 months after conventional treatment (furosemide, carvedilol, angiotensin-converting-enzyme inhibitor and thiamazole administration). This patient represents an exceptional case, as overt congestive heart failure with left ventricular dilatation and depressed ventricular ejection fraction is not a common finding in patients with hyperthyroidism, let alone patients with subclinical hyperthyroidism and no underlying heart disease.