Although the role of the heart in hyperthyroidism has attracted the attention of clinicians since Parry's description of exophthalmic goiter in 1825,1 little accord has been reached as to the electrocardiographic manifestations of this condition. All observers agree that tachycardia and various arrhythmias may be attributed to the thyrotoxic state, but they do not agree on other findings.
In an attempt to determine what electrocardiographic abnormalities may be found in hyperthyroidism, a study was made of adult hyperthyroid patients observed in the thyroid clinic of the University of California Hospital from July 1935 through April 1942. Electrocardiograms were taken on 168 of 484 patients during the period of hyperthyroidism. All patients were seen by one observer (M. H. S.), and all electrocardiograms were interpreted by another observer (F. L. C.). In some cases the electrocardiographic studies were made because of the clinical diagnosis of thyrotoxic heart disease, especially as