Predictors and Risk Scores for New Atrial Fibrillation After Coronary Artery Bypass Grafting

Abstract

Background: New atrial fibrillation (AF) is a common complication after cardiac surgery, and is associated with increased length of hospital stay, morbidity and mortality. Identifying high risk patients may allow a targeted approach to preventing new AF. We evaluated the risk factors of and performance of risk models at predicting new AF after coronary artery bypass grafting (CABG). Methods: All patients without preoperative AF undergoing isolated CABG at Auckland City Hospital from July 2010-June 2012 were included. The prognostic utility of the AF risk index by El-Chami et al., 2012, CHADS2, CHA2DS2-VASc, EuroSCOREs and STS Score for new AF after CABG was assessed. Results: There were 757 (of 818) CABG patients without preoperative AF, mean age 64.0+/-10.0 years and 157 (20.7%) females. Postoperative AF occurred in 179 (23.7%), and was associated with prolonged intensive care (p = 0.012) and hospital stay postoperatively (p < 0.001). Independent predictors of new AF included increased age, weight, congestive heart failure and three-vessel coronary disease. Areas under the curve (95% confidence intervals) for predicting new AF were El-Chami index 0.600 (0.553-0.647), CHADS2 0.559 (0.512-0.606), CHA2DS2-VASc 0.594 (0.547-0.642), logistic EuroSCORE 0.594 (0.545-0.643), EuroSCORE II 0.546 (0.498-0.595) and STS Score 0.584 (0.535-0.634). Conclusion: New AF after CABG was common, and associated with prolonged hospital stay, but was modestly and suboptimally predicted by AF and cardiac surgery risk models. More accurate scores need to be developed to guide clinical practice.