Prolongation of the P-R interval has been reported in uncomplicated hyperthyroidism,1-5 and some of the patients show, in addition, large and tall P waves in leads II, III, and aVF.
Transient complete heart block has been described also in hyperthyroid patients, particularly in association with acute inflammatory diseases.6-11 Electrocardiographic abnormalities usually disappear when the patients become euthyroid.
We are reporting the cases of two hyperthyroid patients without signs of heart disease who had first-degree heart block with tall and large P waves; in one of these patients, a left bundle-branch block and a transient complete heart block with Stokes-Adams episodes also occurred without clear-cut evidence of acute inflammatory disease.
Both patients eventually showed a normal electrocardiographic pattern when they became euthyroid.
PATIENT SUMMARIES
Patient 1.
—A 19-year-old woman was admitted with symptoms of weakness, fatigue, fine tremors, and palpitations. She had been found to be hyperthyroid one