ATRIAL-FIBRILLATION AFTER CORONARY-ARTERY BYPASS-GRAFTING IS ASSOCIATED WITH SYMPATHETIC ACTIVATION

Background. We prospectively investigated the role of sympathetic acti vation in the etiology of atrial fibrillation following coronary arter y bypass grafting. Methods. Continuous ambulatory monitoring was perfo rmed for 80 hours in 131 patients after coronary artery bypass graftin g. Right atrial plasma norepinephrine levels were assessed preoperativ ely and every 4 hours for 48 hours postoperatively. Results. Of the 13 1 patients, 50% (65) had development of atrial fibrillation and 36% (4 7) required treatment. Onset of atrial fibrillation was preceded by a significant increase in sinus rate and atrial ectopic activity. On mul tivariate logistic regression, elevated mean postoperative norepinephr ine levels (5.78 +/- 2.83 versus 3.57 +/- 1.31 nmol/L; p < 0.0001), in creased age (68.9 +/- 5.7 versus 63.8 +/- 8.7 years; p = 0.02), and de creased postoperative magnesium levels (0.79 +/- 0.09 versus 0.83 +/- 0.10 mmol/L; p = 0.02) were independently associated with the occurren ce of atrial fibrillation. Conclusions. Elevated norepinephrine levels suggest that sympathetic activation may be important in the pathogene sis of atrial fibrillation after coronary artery bypass grafting, and this underlines the importance of beta-adrenoceptor blockade as prophy laxis.