[Pathogenesis of cardiac insufficiency in thyrotoxicosis]

The purpose of the work was to study some problems relating to the pathogenesis of cardiac insufficiency in patients with thyrotoxicosis. To do this a total of 108 patients suffering from thyrotoxicosis with varying degree of severity and aged from 17 to 59 were examined. In addition to the general clinical examination vectoro-, poly- and mechanocardiography was employed. The resulting findings ascertained two possible ways for the development of cardiac insufficiency in patients under consideration. One of them is cardiac hyperfunction that comes to the forefront. In this case the myocardial changes are of a stage-wise nature. The myocardial contractility at the onset of the affection is up, a slight hypertrophy is developing, chiefly, of the outflow passages. As the disease progresses further hypertrophy gains in intensity and dilation of the heart comes in as an intercurrent factor. At this time the contractile function of the myocardium is still unaffected and the patients are at a stage of compensation. With progressing dystrophy and wearing away of the myocardium its contractility is declining and signs of cardiac incompetence appear. Such a development is characteristic of patients with severe course of thyrotoxicosis, long-standing disease and frequent relapses. Of the other way is typical cardiac hyperfunction of low intensity. To the forefront come dystrophic alterations in the myocardium unaccompanied by hypertrophy, and in this case cardiac insufficiency is of latent nature. Such alterations are seen to occur with a milder course of thyrotoxicosis, with the disease of short duration. Dynamic observations bear proof to a reversible nature of hypertrophy and dystrophy of the myocardium.