Body mass index predicts new-onset atrial fibrillation after cardiac surgery

Objective: New-onset postoperative atrial fibrillation (POAF) after cardiac surgery is associated with increased morbidity and mortality. Since obesity is becoming increasingly prevalent, identifying body mass index (BMI) as a risk factor for POAF could be of importance. The aim of our study is to investigate the effect of BMI on POAF, independent of other risk factors. Methods: We analyzed data of 6788 men and 2560 women who underwent coronary artery bypass grafting, valve surgery, or a combination of both, and who had no history of atrial fibrillation. Men and women were analyzed separately because risk factors of POAF were expected to be distributed unequally over both sexes. Results: The independent effect of gender was analyzed in a combined model. POAF occurred in 2517/9348 (27%) of patients. Multivariate logistic regression analyses showed that BMI (odds ratio (OR) 1.03; 95% confidence interval (CI): 1.01-1.04; p <0.001 in men and OR 1.03; 95% CI: 1.02-1.05; p <0.001 in women), age (OR 1.06; 95% CI: 1.05-1.07; p <0.001 in men and OR 1.05; 95% CI: 1.04-1.06; p <0.001 in women), valve surgery compared to coronary surgery (e. g., mitral valve surgery compared to coronary artery bypass grafting: OR 3.4; 95% CI: 2.4-4.6; p <0.001 in men and OR 2.9; 95% CI: 2.0-4.3; p <0.001 in women) and male gender (OR 1.23; 95% CI: 1.09-1.38; p = 0.001) were the only independent risk factors for POAF, whereas chronic obstructive pulmonary disease, hypertension, off-pump coronary artery bypass grafting, extra corporal circulation time, and transfusion of blood products were not. Conclusion: Body mass index, age, undergoing valve surgery and male gender, are independent risk factors for POAF.