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August 1975

Heart Block and HyperthyroidismReport of Two Cases

Arch Intern Med. 1975;135(8):1091-1095. doi:10.1001/archinte.1975.00330080093015

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 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

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