Background: In older patients who are known to be at greater risk for atrial fibrillation, we aimed to determine whether patients who develop atrial fibrillation-flutter (AF) after major thoracic surgery have an exaggerated white blood cell (WBC) count in response to surgical stress compared with those who do not develop AF.
Methods: Using a prospective database, 272 patients 60 years or older who were in sinus rhythm before surgery and had elective lobectomy, pneumonectomy, or esophagectomy were studied. Patients did not receive perioperative medications to prevent AF. Clinical characteristics and preoperative 12-lead electrocardiogram were examined and WBC counts were recorded for patients prior to and for up to five days after surgery.
Results: Atrial fibrillation-flutter was observed in 74 of 272 (27%) patients a median of 3 days after surgery. The increase in WBC count from preoperative to postoperative day 1 and age were jointly significant predictors of AF by multiple logistic regression (area under the receiver operating characteristic curve = 0.69). Using this model, a twofold increase in WBC from presurgery to postoperative day 1 corresponded to a 3.3-fold increase in the odds of developing AF (95% confidence interval [CI] 2.0 to 8.3) and for each 10 year increase in age, a 1.8-fold increase in risk of AF (95% CI 1.1 to 2.8) was seen.
Conclusions: Increments in WBC were greater in patients with AF and coincided with the peak onset of AF. These prospective data support an important role for stress-mediated autonomic mechanisms in the pathogenesis of AF after major thoracic surgery. We aim to examine further whether WBC elevations on postoperative day one can help further risk stratify patients younger than 60 years or those with the highest risk who could benefit from one or more AF prevention strategies.