A case of thyrotoxicosis and reversible systolic cardiac dysfunction.

A woman with congestive heart failure and reduced left ventricular ejection fraction associated with hyperthyroidism is reported. Congestive heart failure resolved and left ventricular ejection fraction normalized within three weeks of treatment of her hyperthyroidism. The literature on previously reported cases of reversible systolic heart failure associated with hyperthyroidism is reviewed and the possible mechanisms leading to systolic dysfunction and congestive heart failure in thyrotoxicosis are discussed. One such mechanism may be the action of thyroid hormone on altering gene expression in cardiac cells; another could be the chronic tachycardia associated with thyrotoxicosis. Although it is a not a common cause of systolic heart failure, thyrotoxicosis should be considered in the differential diagnosis of cardiomyopathies because it is a potentially reversible cause.