James B. Seward, MD: From the Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota.

We assessed preoperative cardiac physiology using echocardiography in patients undergoing cardiac surgery to identify predictors of postoperative atrial fibrillation. Subjects with enlarged left atrial volume had a 5-fold greater risk of postoperative atrial fibrillation, independent of age and other risk factors, than those without enlarged left atrial volume. Left atrial volume appears to be a powerful tool to stratify patients according to risk before surgery and to effectively target preventive therapy.