The heart and hypothyroidism.

Summary The association of hypothyroidism with heart disease is reviewed. The. relative raritY" of cardiac failure due to hypothyroidism is stressed, and structural abnormalities of the heart due to hypothyroidism are discussed. The clinical management of hypothyroid patients with heart disease is described. S AIf Med J 1983; 63: 564-565. Hypothyroidism may initiate cardiac disease or worsen that which alread\' exists. Treatmenr of the cardiac problem is influenced by the thyroid disorder and vice versa. We recenrly saw a patienr with hypothyroidism who presenred with cardiomyopathy and severe hean failure resistanr to treatment with digitalis and diuretics. This c~se focused our attention on the problems of management of hypothyroidism complicated by hean disease. The clinical presentation and management ofsuch patients are re\·iewed. Myocardial function Graettinger el al. I have found that resting cardiac output is reduced in hypothyroid patients but that cardiac output, stroke volume and pulse rate increase normally during exercise. This finding implies that cardiac function is still normal, i.e. with the reduction in oxygen requiremenrs and metabolism there is a parallel reduction in cardiac function. It is generally accepted that cardiac function in hypothyroid patients is in keeping with their. metabolic requirements. Treatment with thyroxine reduces myocardial size to normal,2.3 a process which may take from 3 weeks to ID monrhs. Even when the hean is functionally normal, . histological changes in the cardiac muscle have been reponed. The prognostic implications of these changes are not quite clear. The heart may be dilated and hypenrophied when the patient is first seen. 2 Hypothyroid patients often have symptoms compatible with those of heart failure such as tiredness, dyspnoea and even orthopnoea. Clinical signs ofhypothyroidism which may be confused with heart failure include oedema, ascites, cardiomegaly and pleural effusions. Since hypothyroidism is a rare cause of heart failure other causes of heart failure must be excluded in such patients. 2 . 3 According to