Do cardiac neuropeptides play a role in the occurrence of atrial fibrillation after coronary bypass surgery?

Background: One of the potential mechanisms to explain the occurrence of postoperative atrial fibrillation (AF) is imbalance of autonomic nervous system tone. The myocardium is innervated not only by cholinergic and adrenergic nerves but also by peptidergic nerves that synthesize and secrete neuropeptides. To investigate the possible role of cardiac neuropeptides in the development of AF after coronary artery bypass grafting (CABG), we analyzed the plasma levels of substance P (SubP), neuropeptide Y (NPY), and angiotensin II (Ang II) in patients who underwent elective on-pump CABG.

Methods: This prospective study group included 83 consecutive patients scheduled for elective, on-pump CABG. Depressed left ventricular (LV) function (ejection fraction [EF] less than 0.30), concomitant cardiac procedures, history of atrial fibrillation, second or third degree atrioventricular block, implanted pacemaker, postoperative myocardial infarction, use of class I or III antiarrhythmic drug, and hemodynamic deterioration were exclusion criteria. Preoperative and postoperative serum levels of SubP, NPY, and AngII were measured by radioimmunoassay technique.

Results: Postoperative AF occurred in 27 patients (32.5%). Using multivariate logistic regression analyses, only a decrease in SubP level (odds ratio [OR] = 1.87, 95% confidence interval [CI] = 0.767 to 0.99, p = 0.031) and an increase in AngII level (OR = 2.61, 95% CI = 1.002 to 1.021, p = 0.023) after CABG were found to be independently associated with AF. Increased age (p = 0.02), diabetes mellitus (p = 0.023), preoperative use of beta blocker (p = 0.024), proximal right coronary artery involvement (p = 0.024), low preoperative sodium levels (p = 0.023), low LVEF (p = 0.013), and increased mitral E wave deceleration time (p = 0.044) were also associated with AF.

Conclusions: These results indicate that the increase in AngII and the decrease in SubP after CABG may play a role in the occurrence of postoperative AF. Further studies are needed to define the physiologic and pathologic relevance of these substances at the occurrence of AF in patients who undergo CABG.