title: The relative importance of left atrial function versus dimension in predicting atrial fibrillation after coronary artery bypass graft surgery.
abstract: 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 x 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 chi2 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 cm(2) 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.
authors.affiliation: Department of Medicine, Section of Cardiac Electrophysiology, and Cardiovascular Research Institute, University of California, San Francisco 94143, USA. nakai@medicine.ucsf.edu
authors.forename: Toshiko
authors.initials: T
authors.lastname: Nakai
authors.forename: Randall J
authors.initials: RJ
authors.lastname: Lee
authors.forename: Nelson B
authors.initials: NB
authors.lastname: Schiller
authors.forename: Wayne H
authors.initials: WH
authors.lastname: Bellows
authors.forename: Samir
authors.initials: S
authors.lastname: Dzankic
authors.forename: John
authors.initials: J
authors.lastname: Reeves
authors.forename: Joseph
authors.initials: J
authors.lastname: Romson
authors.forename: Scott
authors.initials: S
authors.lastname: Ferguson
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Leung
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001281:Atrial Fibrillation / Q000000981:diagnostic imaging / Q000209:etiology*; D016279:Atrial Function, Left; D001026:Coronary Artery Bypass / Q000009:adverse effects*; D017548:Echocardiography, Transesophageal; D005260:Female; D006325:Heart Atria / Q000000981:diagnostic imaging; D006801:Humans; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011446:Prospective Studies; D012044:Regression Analysis