Association of the Systemic Inflammation Response Index With Atrial Fibrillation Recurrence After Catheter Ablation

Abstract Background Systemic inflammation contributes to atrial remodeling and may influence atrial fibrillation (AF) recurrence after catheter ablation. The systemic inflammation response index (SIRI), calculated as neutrophil count × monocyte count / lymphocyte count, integrates inflammatory activity and immune status. We investigated the association between baseline SIRI and AF recurrence after catheter ablation. Methods This retrospective cohort included 504 adults with paroxysmal or persistent AF who underwent catheter ablation between July 2023 and December 2024. The primary outcome was atrial tachyarrhythmia recurrence lasting at least 30 seconds after a 3-month blanking period during 12-month follow-up. Multivariable logistic regression, restricted cubic spline analysis, receiver operating characteristic analysis, DeLong testing, integrated discrimination improvement (IDI), and category-free net reclassification improvement (NRI) were performed. Results AF recurrence occurred in 140 patients (27.8%). Each 1-standard deviation increase in SIRI was associated with recurrence in univariable analysis (odds ratio [OR], 1.35; 95% confidence interval [CI], 1.10–1.65; P = 0.003) and remained independently associated after adjustment for relevant variables (adjusted OR, 1.24; 95% CI, 1.00–1.54; P = 0.045). Restricted cubic spline analysis suggested a nonlinear association. Adding SIRI to the base clinical model increased the area under the curve from 0.704 to 0.713 without a significant DeLong difference, although IDI and NRI improved. Adding SIRI and C-reactive protein increased the area under the curve to 0.732 and significantly improved DeLong, IDI, and NRI results. Conclusions Higher baseline SIRI was independently associated with AF recurrence after catheter ablation. Its incremental value alone was modest, whereas combining SIRI with C-reactive protein provided greater improvement.