The Relationship Between the Systemic Immune Inflammatory Index and Atrial Fibrillation in Heart Failure with Preserved Ejection Fraction

Background: Immunopathological dysregulation has been implicated as a unifying substrate for both atrial fibrillation (AF) and heart failure with preserved ejection fraction (HFpEF), 2 conditions that cluster with disproportionate frequency in clinical cardiology practice. Systemic immune-inflammation index (SII)—a hematological index derived from the ratio of platelet–neutrophil product to lymphocyte count—has garnered increasing attention as a low-burden inflammatory surrogate. The capacity to discriminate AF from sinus rhythm was investigated in an outpatient cohort with HFpEF.

Methods: A retrospective analysis was conducted on 207 HFpEF outpatients (January 2024-January 2025) stratified by resting electrocardiogram rhythm: sinus rhythm (group 1, n = 105) vs. AF (group 2, n = 102). Independent AF predictors were identified through multivariate binary logistic regression.

Results: Four variables independently predicted AF on multivariate analysis: SII (P = .04), age (P = .010), left atrial diameter (P < .001), and systolic pulmonary artery pressure (P < .001). At an optimal SII threshold of 584.64, sensitivity reached 79.4% and specificity 59% for AF prediction (AUC = 0.727, 95% CI = 0.658-0.796, P < .001).

Conclusion: Systemic immune-inflammation index constitutes a cost-neutral, universally derivable hematological parameter with meaningful clinical utility for AF risk stratification within the HFpEF phenotype. Patients harboring pronounced SII elevation warrant heightened arrhythmia vigilance through serial 12-lead recordings and extended ambulatory electrocardiographic monitoring—should be considered in HFpEF patients with markedly elevated SII to facilitate timely AF detection.

Cite this article as: Şentürk B, Kış M, Çöllüoğlu T, et al. The relationship between the systemic immune inflammatory index and atrial fibrillation in heart failure with preserved ejection fraction. Eurasian J Med. 2026, 58(4), 1589, doi: 10.5152/ eurasianjmed.2026.261589.