A CORRELATION OF CLINICAL AND HEMODYNAMIC STUDIES IN PATIENTS WITH HYPERTHYROIDISM WITH AND WITHOUT CONGESTIVE HEART FAILURE *

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Abstract
In 14 patients without congestive failure the hemodynamic responses during exercise were qualitatively normal despite the fact that 6 had antecedent heart disease. In the 7 patients who had been in congestive failure, the absolute level of cardiac output was normal in 4 and markedly elevated in 3. All had inadequate responses of the cardiac output to exercise. Atrial fibrillation occurred only in the patients with congestive failure or with antecedent heart disease. From these studies it is concluded that congestive heart failure may occur during the course of thyrotoxicosis by several mechanisms: (1) myocardial reserve may be reduced by antecedent heart disease, (2) thyroxin may transiently reduce the myocardial reserve of the heart, and (3) the increased circulatory load of the disease may apparently overcome the reserve of even the normal heart. When the decrease in myocardial reserve in the presence of the increased load is the major abnormality, the cardiac output tends to be in the "normal" range. When the decrease in reserve is less and the increase in circulatory load greater, the cardiac output may be remarkably high. The peripheral circulatory load in thyrotoxicosis is hemodynamically similar to that of a systemic arterio-venous fistula.