Abstract Body: Background: Inflammatory mechanisms play a significant role in the development and progression of idiopathic pulmonary arterial hypertension (IPAH). The systemic immune-inflammation index (SII) is thought to be an important factor in determining the prognosis of heart failure patients. However, the significance of the SII has not yet been fully clarified in IPAH patients. Therefore, the aim of this study was to determine the association between the SII and the prognosis of IPAH patients and to explore whether dynamic assessments of the SII was superior to measurements at a single time point for predicting patient prognosis.
Methods: Consecutive patients who underwent right heart catheterization and had at least two SII measurements from January 2016 to January 2025 were included. The SII was calculated as the platelet counts × neutrophil counts/lymphocyte counts. Changes in the SII (ΔSII) were defined as the SII at the second examination time − the SII at the first examination time. The main outcome measure was clinical deterioration. Cox proportional hazard models were used to examine the associations between the SII and clinical deterioration.
Results: A total of 408 patients with IPAH whose two SII measurements and follow-up data were included in this study. The SII was positively associated with indicators such as B-type natriuretic peptide, right ventricular end-diastolic diameter, mean pulmonary arterial pressure, and pulmonary vascular resistance. Conversely, the SII had inverse relationships with the 6-minute walk distance. Multivariate Cox analysis revealed that a high SII was an independent risk factor for clinical worsening [hazard ratio (HR): 2.485, 95% confidence interval (CI): 1.673–3.297; P= 0.009] after adjusting for covariates. Patients with a ΔSII ≥ 126 had an over four times increased risk of adverse clinical events compared with their counterparts after adjusting for confounders (HR: 4.112, 95% CI: 1.463–6.761; P= 0.005). The relationship between the SII and clinical worsening was further verified by propensity score matching analysis.
Conclusions: The SII may be an easily accessible and cost-effective tool for identifying the severity and prognosis of IPAH. More importantly, changes in the SII were also independently correlated with prognosis in patients with IPAH, irrespective of the baseline SII. Repeated assessment of the SII contributes to better identification of IPAH patients with an increased risk of adverse clinical events.