Atrial fibrillation after coronary artery bypass grafting is associated with sympathetic activation

BackgroundWe prospectively investigated the role of sympathetic activation in the etiology of atrial fibrillation following coronary artery bypass grafting. Methods.: Continuous ambulatory monitoring was performed for 80 hours in 131 patients after coronary artery bypass grafting. Right atrial plasma norepinephrine levels were assessed preoperatively and every 4 hours for 48 hours postoperatively. Results.: Of the 131 patients, 50% (65) had development of atrial fibrillation and 36% (47) required treatment. Onset of atrial fibrillation was preceded by a significant increase in sinus rate and atrial ectopic activity. On multivariate logistic regression, elevated mean postoperative norepinephrine levels (5.78 ± 2.83 versus 3.57 ± 1.31 nmol/L; p < 0.0001), increased age (68.9 ± 5.7 versus 63.8 ± 8.7 years; p = 0.02), and decreased postoperative magnesium levels (0.79 ± 0.09 versus 0.83 ± 0.10 mmol/L; p = 0.02) were independently associated with the occurrence of atrial fibrillation. Conclusions.: Elevated norepinephrine levels suggest that sympathetic activation may be important in the pathogenesis of atrial fibrillation after coronary artery bypass grafting, and this underlines the importance of β-adrenoceptor blockade as prophylaxis.