[Contractile function of the myocardium of the right ventricle in thyrotoxicosis]

The functional condition of the myocardium of the right ventricle was studied in 98 patients suffering from thyrotoxicosis and in 28 healthy persons. The pressure in the pulmonary artery, the tension index of the myocardium and the frequency of cardiac contractions proved to increase against the background of an excess of thyroid hormones in the organism. The contractility index of the myocardium, the volume velocity of the ejection, the rate of displacement of the wall of the ventricle during blood expulsion increased at the early stages of the disease, and later became lowered. Under experimental conditions the initial period of thyoidin intoxication was characterized by increased work of the right ventricle. The electron microscopic picture corresponding to this phase of the process pointed to the injurious action of the thyroid gland hormones on the mitochondria. The greatest increase in the functional intensity of the myocardium of the right ventricle was reached on the 14th day of the experimental thyroidin intoxication. The ultrastructural changes recorded at this period reflected the growing hyperfunction of the mitochondria and the development of destructive changes in the contractile aparatus of the myocytes.