THE EFFECTS OF PROPRANOLOL AND VERAPAMIL ON HYPERTHYROID HEART SYMPTOMS AND FUNCTION, ASSESSED BY SYSTOLIC-TIME INTERVALS

The effects of acute and chronic administration of propranolol and verapamil on heart rate and systolic time intervals were studied in 10 hyperthyroid patients and 10 normal subjects, both groups without signs of cardiovascular or pulmonary disease. In normal subjects iv propranolol reduced heart rate significantly, and both drugs increased the total electromechanical systole significantly without difference between the drugs. This effect was insignificant when the drugs were given orally. In hyperthyroid patients both drugs reduced heart rate significantly in acute and chronic administration. and no difference between the two drugs was found. Neither drug altered cardiac contractility as assessed by systolic time intervals. These results indicate that the metabolic effects of thyroid hormone on contractility were unaltered and unblocked by the drugs. None of the participants developed signs of heart failure. Verapamil can thus be used as an alternative to propranolol in the treatment of tachycardia in hyperthyroidism.