The Relationship Between Atrial Fibrillation and the Systemic Immune Inflammation Index in Well-Controlled...

Background: Hypertension (HT) and atrial fibrillation (AF) are frequently coexisting conditions, with inflammation being a crucial pathophysiological mechanism shared by both. The systemic immune-inflammation index (SII), a newly introduced combined inflammatory marker, includes the parameters of platelets, neutrophils, and lymphocytes. Current literature lacks studies investigating the relationship between SII and newly developed AF in patients with controlled HT. Therefore, this study aimed to explore the association of SII with AF in hypertensive patients on anti-hypertensive therapy. Methods: This retrospective case-control study included 68 hypertensive patients with controlled blood pressure who underwent 24 h Holter monitoring. Patients were divided into two groups based on the presence of atrial fibrillation (AF-positive, n = 32; AF-negative, n = 36). SII values were calculated from complete blood counts. Demographic, clinical, and laboratory characteristics were compared between groups. Correlation analysis was performed to assess associations of SII with clinical parameters. Multivariable logistic regression identified independent predictors of AF. Optimal cut-off values for systemic immune-inflammation index and age were determined through receiver operating characteristic analysis. Results: Patients with AF were significantly older than those without AF (p < 0.01). The systemic immune-inflammation index was significantly higher in patients with atrial fibrillation (p = 0.02). Patients with AF also had higher heart rates (p = 0.04) and creatinine levels (p < 0.01). SII showed a moderate positive correlation with C-reactive protein (CRP) (r = 0.393, p < 0.01) and a weak correlation with heart rate (r = 0.251, p = 0.039). In multivariable analysis, SII (OR: 1.024, p = 0.04) and age (OR: 1.130, p < 0.01) was independently associated with AF. Receiver operating characteristic analysis determined an SII cut-off of 483.0 with a sensitivity of 53.1% and specificity of 52.8%. The age cut-off was found to be 63 years with sensitivity and specificity being 62.5% and 66.7%, respectively. Conclusions: The systemic immune-inflammation index was significantly elevated in newly diagnosed AF patients with well-controlled hypertension and was an independent predictor of AF. It is a simple, readily available biomarker that may assist in identifying hypertensive patients at high risk for the development of AF. These results should be validated in future studies, and the role of inflammation in the pathogenesis of atrial fibrillation should be further explored.