Echocardiographic studies on the relationship between atrial fibrillation and atrial enlargement in patients with hyperthyroidism of Graves' disease.

In order to study the relationship between the left atrial size and atrial fibrillation (AF) in patients with thyrotoxicosis, 92 patients with Graves' disease were examined. Out of 92 patients (23 men and 69 women, age 7-71 years), 21% had AF: 31% of the patients older than 40 years had AF whereas none of the patients younger than 40 years had AF. Echocardiography revealed that the left atrial enlargement (more than 40 mm) exist in 7% of patients younger than 40 years, in 2% of those older than 40 years without AF and 94% of those older than 40 years with AF. Serum T3 and T4 were higher in the patients with AF than in those without AF when patients older than 40 years were analyzed.