The predictive role of renal function and systemic inflammation on the onset of de novo atrial fibrillation after cardiac surgery

BACKGROUND: The association between postoperative atrial fibrillation (POAF) and renal function was previously grounded in patients undergoing coronary artery bypass grafting through unknown mechanisms. We aim to investigate the association between renal function and POAF in a cohort composed mostly of patients undergoing valve surgery and to explore the role of inflammation as a pathogenic mechanism linking renal dysfunction and arrhythmogenesis. METHODS: Altogether 444 patients who underwent cardiac surgery without previous history of atrial fibrillation were analysed. Serum creatinine and high sensitivity C-reactive protein (hs-CRP) concentrations were obtained at baseline and on the 3rd, 8th and 15th postoperative day; estimated glomerular filtration rate (eGFR) was calculated by the Modified Diet Renal Disease (MDRD) formula. Patients were divided into three groups on the basis of baseline eGFR. RESULTS: Overall, 173 (39%) patients developed POAF, 29.5% in the group with normal eGFR (≥90 ml/min/1.73 m(2)), 43.3% among patients with eGFR 60-90 ml/min/1.73 m(2) and 55.6% in the group with eGFR ≤60 ml/min/1.73 m(2). Patients developing POAF had lower eGFR on all the samples. At baseline preoperatively hs-CRP levels did not differ in the two groups.On multivariate analysis, age and eGFR were identified as independent predictors of POAF. The risk of POAF progressively increased from mild impairment (odds ratio (OR) 1.59, 95% confidence interval (CI) 1.01-2.50) to severe reduction of renal function (OR 2.35, 95% CI 1.25-4.48). CONCLUSIONS: Age and eGFR were identified as the strongest predictors of POAF in a population largely composed of valve surgery patients. Renal function, even from early stage, is independently associated with the increasing risk of developing POAF.