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First-Degree Heart Block Associated With Thyrotoxicosis

Arch Intern Med. 1963;112(4):488-490. doi:10.1001/archinte.1963.03860040084006.
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Patients with uncomplicated hyperthyroidism have been observed to have prolongation of the P-R interval.1-3 Except for a report by Goodall and Rogers, the incidence of these two concomitant findings is rare.5-8 In most references the electrocardiographic findings after successful therapy are not reported. Acute inflammatory diseases, particularly tonsillitis and respiratory tract infections, in patients with or without hyperthyroidism, have been associated with transient abnormalities of atrioventricular (AV) conduction.7,9,10 Blizzard and Rupp1 reported five hyperthyroid patients without heart disease with prolongation of the P-R interval, and four of this group had a normal AV conduction when euthyroid. The following report documents this unusual electrocardiographic pattern in a hyperthyroid subject without heart disease.

Report of a Case  A 37-year-old Negro female was admitted to Montefiore Hospital on Oct 5, 1961, with symptoms of palpitations, shortness of breath, paroxysmal nocturnal dyspnea, weakness, fatigue, tremors, diarrhea, heat intolerance, and the


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