Comparison of the Action of Ouabain on the Heart in Hypothyroid , Euthyroid and Hyperthyroid Dogs

• Although, it is assumed that digitalis glycosides are relatively ineffective in heart failure and atrial fibrillation associated with disorders of thyroid gland function," there is little experimental work to support this belief. Frye and Braunwald observed that administration of triiodothyronine to euthyroid and hypothyroid patients with chronic atrial fibrillation increased the dose of cardiac glycosides required to slow the ventricular rate. No experimental work has been done on the effect of cardiac glyeosides on cardiac contractile force following changes in thyroid function. That disorders of thyroid function may alter the tosicity of digitalis is also a common belief. Digitalis intoxication is considered to occur more frequently in patients with thyrotoxicosis than in those in a euthyroid state.''" Caution in the use of digitalis in such cases has been, therefore, advisable. Older experimental work on the influence of altered thyroid state on digitalis toxicity, which has been reviewed by Lendle in 1935, suggests that the toxieity of digitalis is increased in hyperthyroidism and decreased in hypothyroidism. However, we know of no recent experimental work concerned with this problem.