Oxidative Stress and Postoperative Atrial Fibrillation: A Systematic Review and Meta-Analysis.

Postoperative atrial fibrillation (POAF) is the most common arrhythmia after cardiac surgery and is linked to higher mortality and hospitalizations. Oxidative injury may contribute to its development; therefore, we aimed to systematically evaluate the relationship between oxidative stress biomarkers and POAF. MEDLINE, Embase, and the Cochrane Library were searched from inception to August 2026 for studies reporting oxidative stress biomarkers and POAF in adults undergoing cardiac surgery. Altogether, 31 studies (4,983 patients) were included; most were at high risk of bias by QUIPS assessment. We pooled similar studies using random-effects meta-analysis, compared associations between atrial and circulating measurements using a three-level model with cluster-robust inference, and summarized the remaining studies by effect direction. Pooled POAF incidence was 30.4% (95% CI 27.4 to 33.5). Atrial oxidative stress biomarkers were higher in patients who developed POAF (Hedges g 0.89, 95% CI 0.45 to 1.32), but blood levels of the same biomarker showed no statistical significance (g 0.13, 95% CI -0.04 to 0.30; between-compartment difference of 0.76, p = 0.005). Among individual markers, preoperative malondialdehyde differed only modestly between groups, while circulating markers increased postoperatively. Atrial oxidase and pericardial myeloperoxidase activity showed the largest adjusted associations with POAF. Oxidative-stress associations with POAF depend on sampling site and timing. Atrial tissue measures show stronger associations than preoperative blood biomarkers, while early postoperative pericardial and circulating markers may reflect reperfusion injury. Because the evidence is heterogeneous, standardized prospective studies are needed to validate these biomarkers and determine their clinical utility.