Operative Factors that Contribute to Post-Operative Atrial Fibrillation: Insights from a Prospective Randomized Trial

Atrial fibrillation (AF) is the most common complication following cardiac surgery and is associated with significant increases in postoperative morbidity, length of stay and cost of care. In a randomized study we assessed the impact of coronary artery bypass grafting (CABG) without cardiopulmonary bypass (CPB) (off-pump, n = 100), compared to conventional (on-pump, n = 100) CABG, on the frequency of postoperative AF. Arrhythmias were detected using an automated arrhythmia detector for the first 72 hours following surgery and by four hourly clinical observations thereafter. AF was defined as an irregular narrow complex rhythm (in the absence of bundle branch block) with absence of discrete P waves lasting greater then 10 minutes. There was a significant reduction in the incidence of postoperative AF in the off-pump group (11% versus 45%, P < 0.001) in addition to significant reductions in blood usage, postoperative pneumonia, inotrope requirements, and hospital and intensive care unit stay. Univariate analysis identified all these variables as risk factors for AF, however multivariate regression analysis identified CPB and cardioplegic arrest as the only independent predictor of postoperative AF (OR 7.4; 95% CI 3.4 to 17.9). This study therefore suggests that the inflammatory response to bypass, myocardial ischaemia and atrial cannulation are significant contributory factors to the development of AF following cardiac surgery. In the light of more recent trials it is apparent that this benefit may be most marked in patients with multiple perioperative risk factors for postoperative AF.