[Cardiovascular manifestations of hypothyroidism]

On the basis of a case history, the clinical and paraclinical manifestations of hypothyroidism are reviewed. Exertion dyspnoea without signs of cardiac insufficiency occurs frequently. The minute and stroke volume and heart rate are reduced. The blood pressure may rise (reversible) and hypertension may occur. The function of the left ventricle is reversibly reduced. A tendency to formation of exudates has been observed. X-ray of the thorax may revial massive relatively asymptomatic pleural exudates and cardiomegaly. Pericardial exudate occurs frequently and is demonstrated best by echocardiography. Inter- and intracellular deposits, infiltrations and fibroses have been demonstrated in the myocardium and these probably contribute to some of the non-specific, reversible ECG changes (low voltage, flattening/inversion of T waves, sinus bradycardia). The plasma concentrations of several different enzymes (including creatine kinase (CK), CK-MB and LDH) may be raised in myxoedema. The reason for this is perhaps compromized membrane function in the skeletal muscle cells. The diagnosis of myocardial infarction in myoedema requires that CK-MB constitutes at least 6% of the total CK and that the increase is transient. In patients with coronary sclerosis, substitution treatment should be initiated carefully because the risk of ischaemic symptoms is otherwise considerably increased. It is not elucidated whether the hypothyroidism per se can increase atheroma formation.