CARDIAC LEFT-VENTRICULAR FUNCTION BEFORE AND DURING EARLY THYROXINE TREATMENT IN SEVERE HYPOTHYROIDISM

In some patients with severe hypothyroidism, thyroxine replacement therapy precipitates or aggravates angina pectoris, whereas in other patients angina pectoris is ameliorated or even cured. Cardiac function in eight severely hypothyroid patients was studied by means of radionuclide ventriculography (RNV) at rest and during supine bicycle exercise before thyroxine treatment, and repeated during treatment before and after administration of 160 mg of oral verapamil. There was an exercise-induced fall in left ventricular ejection fraction (LVEF) in two patients before therapy, and in two additional subjects after 17 d on suboptimal doses of thyroxine. Verapamil attenuated the fall and induced a significant increase in LVEF during exercise (P < 0.014). No abnormal regional cardiac wall movement (RWM) was observed. After 2 months of thyroxine treatment, LVEF increased significantly during exercise both before and after verapamil (P < 0.012 and P < 0.005). These findings are indicative of reversible coronary artery dysfunction. We recommend that, if feasible, thyroxine should be supplemented with verapamil during the early phase of treatment.