Preprocedural systemic immune-inflammation index predicts atrial fibrillation recurrence after catheter ablation: A systematic review and meta-analysis

Inflammation plays a significant role in the pathophysiology of atrial fibrillation (AF) and may affect the likelihood of AF recurrence following catheter ablation. The systemic immune-inflammation index (SII), calculated from circulating neutrophils, lymphocytes, and platelets, has emerged as a promising inflammatory biomarker. This meta-analysis aimed to assess the relationship between preprocedural SII and the recurrence of AF post-ablation. We conducted comprehensive searches across PubMed, Embase, Web of Science, Wanfang, and China National Knowledge Infrastructure (CNKI) for longitudinal observational studies reporting the correlation between preprocedural SII and AF recurrence after either radiofrequency or cryoballoon ablation. Risk ratios (RRs) were aggregated using random-effects models to account for heterogeneity. A total of ten cohort studies involving 4,045 patients were included in the analysis. Our findings indicate that a high preprocedural SII is significantly associated with an increased risk of AF recurrence (RR = 2.32, 95% CI 1.68-3.21; I² = 86%). This association remained robust across sensitivity analyses (RR range 2.07-2.53) and showed consistency across predefined subgroups based on sample size (<400 vs. ≥400), age (<61 vs. ≥61 years), sex distribution (<60% vs. ≥60% men), SII cutoff (<510 vs. ≥510), ablation modality (RFCA vs. CBA), follow-up duration (<20 vs. ≥20 months), and study quality (all p for subgroup differences >0.05), although these subgroup analyses were exploratory in nature. Meta-regression did not reveal significant study-level modifiers. Additionally, a further meta-analysis treating SII as a continuous variable demonstrated that each 100-unit increase in SII correlates with a higher recurrence risk (RR = 1.09, 95% CI 1.04-1.13; I² = 43%). In conclusion, elevated preprocedural SII is associated with an increased risk of AF recurrence after catheter ablation, indicating that SII may serve as a potential adjunctive marker of inflammatory status, pending further prospective validation.