Preoperative Alterations in Correlation Properties and Complexity of R–R Interval Dynamics Predict the Risk of Atrial Fibrillation after Coronary Artery Bypass Grafting in Patients with Preserved Left Ventricular Function

Abstract

We evaluated whether there are constant preoperative alterations in nonlinear R-R interval dynamics that associate with the risk of postoperative atrial fibrillation in patients with preserved left ventricular function. We analyzed mean normal-to-normal R-R intervals, short-term scaling exponent of detrended fluctuation analysis (DFA alpha(1)), approximate entropy and entropy of symbolic dynamics (SymDyn En) from 10-minute ECG recordings during rest, paced breathing, and passive tilt performed 1 day before surgery in 67 elective coronary artery bypass grafting patients. Nineteen patients developed postoperative atrial fibrillation. The preoperative DFA alpha(1) was constantly lower in patients developing postoperative atrial fibrillation than in patients remaining in sinus rhythm (P = 0.016); during spontaneous breathing, the DFA alpha(1) was 0.93 +/- 0.33 in patients with atrial fibrillation and 1.13 +/- 0.24 in patients with sinus rhythm. The entropy of symbolic dynamics was higher during the spontaneous breathing in patients with atrial fibrillation than in patients with sinus rhythm (4.72 +/- 0.51 vs 4.36 +/- 0.51, P = 0.012). Higher short-term scaling exponent of detrended fluctuation analysis during the spontaneous breathing period reduced the risk of postoperative atrial fibrillation (OR 0.31 for an interquartile increase in DFA alpha(1), 95% CI 0.13-0.78), while higher entropy of symbolic dynamics increased it (OR 3.16 for an interquartile increase in SymDyn En, 95% CI 1.23-8.10), independently of age and clinical risk factors. The preoperatively altered nonlinear R-R interval dynamics were independent predictors of postoperative atrial fibrillation and might become a useful tool for the risk assessment of atrial fibrillation.