The relative importance of left atrial function versus dimension in predicting atrial fibrillation after coronary artery bypass graft surgery

Background Atrial fibrillation (AF) is a common complication after coronary artery bypass graft (CABG) surgery. The purpose of this study was to determine whether pre-existing left atrial dysfunction is a predictor of postoperative AF compared with other clinical predictors. Methods Ninety-three patients undergoing CABG were prospectively studied. Intraoperatively, transesophageal echocardiography was performed to measure left atrial size, transmitral flow velocity, and other routine parameters. Left atrial function was estimated by the following formula: Atrial INDEX = Transmitral VTI total × LAEF/Left atrial maximal area (where VTI = velocity time integral of E and A waves, LAEF = left atrial ejection fraction). The association of potential clinical predictors with the occurrence of postoperative AF was evaluated by χ2 or Fisher exact tests, followed by stepwise multivariate logistic regression model. P values and odds ratios (OR) with 95% CIs were reported. Significance was set at P < .05. Results Postoperative AF occurred in 28 of 93 patients (30.1%). Patients with postoperative AF were older (67.0 ± 8.3 vs 61.5 ± 9.6 years, P = .0075), had larger left atrial maximal area (14.3 ± 4.6 cm2 vs 10.9 ± 4.3 cm2, P < .001), lower atrial index (0.54 ± 0.56 vs 0.82 ± 0.64, P = .008), larger body surface area (BSA) (OR 57, 95% CI 3.97-827), longer aortic cross-clamp time (OR 1.03, 95% CI 1.00-1.05), and more likely to have a postoperative myocardial infarction (OR 3.28, 95% CI 0.99-10.87) compared with those without AF. By multivariate analysis, only age (OR 1.11, 95% CI 1.04–1.19, P = .002) and atrial dimension (OR 1.75, 95% CI 1.03–2.96, P = .038) were significant independent predictors of postoperative AF. Body surface area also increased the odds of postoperative AF, but the CI was wide (OR 114, 95% CI 4.65–2810, P = .004). Conclusions Our results demonstrate that age and atrial enlargement, rather than atrial function, were independent predictors of postoperative AF. (Am Heart J 2002;143:181-6.)