Updated evidence on peri-operative neutrophil-to-lymphocyte ratio in cardiac surgery: A dual analysis of prognostic and diagnostic value for post-operative atrial fibrillation.

Background: Post-operative atrial fibrillation (POAF) is a frequent complication after cardiac surgery, increasing morbidity. The neutrophil-to-lymphocyte ratio (NLR), a simple marker of systemic inflammation, has been studied as a predictor.

Objective: We aimed to assess the association between NLR and new-onset POAF.

Methods: We systematically searched PubMed, Scopus, Web of Science, and Embase through June 2025 for studies reporting pre-operative or post-operative NLR and incidence of POAF in adult cardiac surgery patients. Diagnostic test accuracy (DTA) was assessed to evaluate the predictive performance of pre-operative NLR for POAF, using pooled sensitivity, specificity, and likelihood ratios. Subgroup analyses and meta-regression were conducted to explore sources of heterogeneity.

Results: 32 studies (20,056 patients) were included. In 27 studies excluding pre-operative atrial fibrillation (13,630 patients), POAF was associated with significantly higher pre-operative NLR (standardized mean difference [SMD] = 0.51; 95% confidence interval [CI]: 0.34-0.67; P < .001; I² = 94.0%). Post-operative NLR was also elevated in POAF patients (SMD = 0.30; 95% CI: 0.13-0.47; P < .001; I² = 70.7%). Among 4 studies including patients with prior atrial fibrillation (6364 patients), no significant association was observed (SMD = 0.04; P = .21). DTA analysis of 12 studies showed pooled sensitivity of 0.52, specificity of 0.71, and diagnostic odds ratio of 3.74 (area under the curve [AUC] = 0.713), indicating moderate diagnostic accuracy.

Conclusion: Elevated NLR is associated with increased risk of POAF. Distinguishing new-onset POAF and accounting for surgical type are essential when evaluating NLR as a predictive biomarker.