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The occurrence of congestive heart failure dur- ing the course of hyperthyroidism has frequently been observed, as has its amelioration after re- establishment of the euthyroid state. The ma- jority of patients in whom congestive failure has appeared have been believed to have myocardial disease of other etiology (1, 2), but the probability that the circulatory load imposed by hyperthy- roidism can cause even the otherwise healthy heart to fail has also been suggested During investigation of the hemodynamic consequences of the endogenous circulatory loads imposed by vari- ous disorders, we have obtained clinical and physi- ologic data in 20 patients with hyperthyroidism, seven of whom were or had been in congestive heart failure. At the time of study we were un- able to determine whether the congestive failure was principally attributable to myocardial damage antedating thyrotoxicosis, to a possibly direct toxic action of thyroxin on the myocardium, or might be due to the circulatory load imposed by this dis- ease overcoming the reserve of an otherwise healthy myocardium. Evaluation of these patients after they had become euthyroid disclosed that only five had residual heart disease. The meas- urements made in these patients with congestive failure differed significantly from those obtained in hyperthyroid patients not in failure; further- more, the patients in whom congestive failure had occurred could be subdivided into two significantly different groups on the basis of the hemodynamic data. It is our purpose in the present paper to
Graettinger et al. (Sat,) studied this question.