Diminished circadian variation in heart rate variability before surgery inpatients developing postoperative atrial fibrillation

Objective - To evaluate the role of the autonomic nervous system for the de velopment of atrial fibrillation (AF) after coronary artery bypass Surgery. Design - Eighty patients without a previous history of AF were included. Th e sympathetic and parasympathetic activity were evaluated by the analysis o f heart rate variability (HRV) in the frequency domain from 24-h Holter rec ordings and by measuring neuropeptides (neuropeptide Y, chromogranin A, chr omogranin B, and pancreatic polypeptide (PP)) and catecholamines, obtained pre- and postoperatively. Results - Preoperatively, patients (36.3%) developing AF postoperatively sh owed a statistically significant less circadian variation in the HRV variab les, the hi gh-f requency (HF) component (p = 0.013) and the low-frequency (LF)/HF ratio (p = 0.007), than patients remaining in sinus rhythm. The HF component and PP, both reflecting parasympathetic activity, and all other v ariables in the frequency domain, decreased significantly after surgery in both patient groups (p < 0.0001). Although catecholamines increased signifi cantly postoperatively in both patient groups, neither catecholamines nor n europeptides expressing sympathetic activity, differed between the two g PP groups. PP was, however, significantly higher in patients with postoperati ve AF than in those with sinus rhythm postoperatively on day 1. Conclusion - The diminished circadian variation in HRV before surgery and t he indirect signs of a higher parasympathetic activity in patients developi ng postoperative AF compared with patients remaining in sinus rhythm, may i ndicate a propensity for AF.