Effects of operation on left atrial size and the occurence of atrial fibrillation in patients with hypertrophic subaortic stenosis.

The relation between left atrial size and atrial fibrillation was examined in 37 patients who had left ventriculomyotomy and myectomy at the National Heart and Lung Institute. Atrial fibrillation was present in 11 of 27 (41%) patients with an echocardiographically measured left atrial dimension greater than 45 mm. No patient with a left atrial dimension less than 45 mm had atrial fibrillation pre or postoperatively. Eleven of 13 patients less than 40 years of age with an abnormal preoperative left atrial dimension had a 10% or greater reduction in left atrial dimension postoperatively. A group of 21 patients 40 years of age or older had an abnormal left atrial dimension preoperatively, and no significant change postoperatively. These results indicate that left ventriculomyotomy and myectomy can produce a significant decrease in left atrial size in younger patients with idiopathic hypertrophic subaortic stenosis. It is hoped that the decrease in atrial size may reduce the risk of atrial fibrillation in these patients.