Left ventricular function in hypothyroidism. Responses to exercise and beta adrenoceptor blockade.

Abstract

The effects of exercise and .beta.-adrenoceptor blockade on left ventricular function were assessed in 8 patients with hypothyroidism before and during thyroxine replacement treatment. Left ventricular ejection fraction, measured by radionuclide ventriculography, was reduced in hypothyroid patients at rest and on exercise. The rise in ejection fraction with exercise was similar in both groups. Pretreatment with i.v. propranolol reduced the ejection fraction at rest 9% in both hypothyroid and euthyroid patients and reduced the rise on exercise. Directional changes in a 2nd index of myocardial contractility based on the shape of the ventricular volume curve paralleled the changes in the ejection fraction. Left ventircular function is therefore reversibly depressed by thyroid hormone deficiency but responses to exercise and .beta.-adrenoceptor blockade are normal. There is no evidence of altered adrenergic sensitivity in the control of myocardial contractility in hypothyroidism.