Systemic Immune‐Inflammation Index is Associated With Tumor Size and Preoperative Cerebrovascular Events in Left Atrial Myxoma

Background Cardiac myxomas are benign tumors associated with potentially serious cerebrovascular complications. The systemic immune‐inflammation index (SII) is a readily available inflammatory marker; however, its relationship with tumor burden and cerebrovascular events in patients with left atrial myxoma remains unclear. This study investigated the associations of SII with tumor size and preoperative stroke or transient ischemic attack (TIA). Methods This single‐center, retrospective study included 120 patients who underwent surgical resection of histopathologically confirmed left atrial myxoma between May 2014 and December 2025. Tumor size was assessed as the largest cross‐sectional area measured by transesophageal echocardiography. SII was calculated from preoperative neutrophil, platelet, and lymphocyte counts. Correlation, multivariable regression, and receiver operating characteristic (ROC) analyses were performed. Results Preoperative stroke/TIA occurred in 17 patients (14.2%). SII was positively correlated with tumor size (ρ = 0.602, p < 0.001) and remained significantly associated with tumor area after multivariable adjustment (β = 0.100 cm 2 per 100‐unit increase, 95% CI: 0.078–0.123; p < 0.001). Patients with larger tumors had a higher prevalence of preoperative stroke/TIA (21.9% vs. 5.4%, p = 0.016). Similarly, cerebrovascular events were more frequent in patients with high SII (≥840) than in those with low SII (32.4% vs. 6.0%, p < 0.001). Both SII (adjusted OR = 1.05 per 100‐unit increase, 95% CI: 1.01–1.09; p = 0.021) and tumor size (adjusted OR = 1.80, 95% CI: 1.05–3.09; p = 0.033) were associated with preoperative stroke/TIA in multivariable analysis. SII demonstrated the highest numerical ROC area (AUC = 0.782), compared with the neutrophil‐to‐lymphocyte ratio (0.746), platelet‐to‐lymphocyte ratio (0.710), and tumor size (0.682). Conclusions SII was significantly associated with tumor size and preoperative cerebrovascular events in patients with left atrial myxoma. As an inexpensive and readily accessible marker, SII may complement echocardiographic assessment, although prospective validation is required.