Postoperative White Blood Cell Count Predicts Atrial Fibrillation after Cardiac Surgery

Abstract

Background: Postoperative atrial fibrillation (AF) occurs in up to 50% of cardiac surgery patients and represents the most common postoperative arrhythmic complication. The etiology of AF after open-heart surgery is incompletely understood and its prevention remains suboptimal. Currently, the role of inflammation and oxidative stress on electrical remodelling is under investigation and recent studies have demonstrated that CRP levels are elevated in atrial fibrillation. The aim of the present study was to investigate the correlation between the postoperative white blood cell (WBC) count as a marker of inflammation and the development of postoperative AF after cardiac surgery. Methods and Results: Patients undergoing elective cardiac surgery in the absence of significant left ventricular dysfunction (n=253; average age 65+/-11 years) were recruited to the present prospective study. 99 patients (39.1%) of the total study population developed AF during the postoperative period. WBC was prospectively assessed in all patients to determine the predictive value of baseline and postoperative WBC count on development of postoperative AF. Baseline and postoperative peak WBC count was 6.8±1.9 K/µL and 6.8±2.2 K/µL (p=0.95), and 16.3±6.5 K/µL and 15±4.2 K/µL (p=0.048) in patients with and without postoperative AF, respectively. However, neither baseline nor peak monocyte count differed significantly between patients with and without postoperative AF (0.43±0.15 K/µL and 0.46±0.46 K/µL [p=0.5], and 0.91±0.3 K/µL and 0.93±0.4 K/µL [p=0.8], respectively). In addition to elevated peak WBC count (above versus below median [odds ratio (OR)=1.8; 95%CI, 1.1 to 2.7; P<0.05], increasing age (above versus below median [OR=2.6; CI, 1.2 to 3.9; P<0.01]), surgery for valvular heart disease (versus coronary artery bypass grafting [OR 2.8; CI, 1.1 to 3.5; P<0.01)]), development of postoperative complications (stroke, infections, unstable hemodynamics [OR=1.9; CI, 1.0 to 7.5; P<0.05]), and perioperative non-use of beta-adrenergic blockers (OR=1.7; CI, 1.1 to 4.9; P<0.05) were identified as independent predictors of postoperative AF by multivariate logistic regression analysis. Conclusions: Cardiac surgery is associated with elevated postoperative WBC count that represents a common marker of inflammation. A more pronounced increase in postoperative WBC counts independently predicts development of postoperative AF. These data provide additional evidence supporting the association between inflammatory response and postoperative AF.