Clinical characteristics of primary SS– and overlap SS–associated pulmonary arterial hypertension: a multicentre retrospective study

OBJECTIVE: The objective of this study was to explore the clinical characteristics and risk factors for adverse outcomes in patients with SS-associated pulmonary arterial hypertension (SS-PAH). METHODS: A retrospective analysis was conducted on SS-PAH patients diagnosed by right heart catheterization (RHC) between March 2013 and March 2024 across four Chinese medical centres. Patients were categorized into primary SS-PAH (pSS-PAH) and overlap SS-PAH groups, based on the presence of additional autoimmune diseases. We compared clinical and demographic data, echocardiographic and haemodynamic parameters, treatment strategies, and event-free survival between the groups. The statistical analyses included t-tests, Wilcoxon rank-sum tests, χ2 tests, Fisher's exact tests, and Kaplan-Meier survival analysis. RESULTS: Overlap SS-PAH was most commonly associated with SLE. Compared with pSS-PAH, overlap SS-PAH patients had a lower proportion categorized as having WHO functional class III-IV, lower pulmonary vascular resistance (PVR), and higher cardiac index. They also showed higher treatment success rates and better event-free survival. However, overlap SS-PAH patients with primary biliary cholangitis (PBC) or autoimmune hepatitis (AIH) had significantly lower 1-year event-free survival rates, older age, and elevated ALP levels. CONCLUSION: Overlap SS-PAH generally has a better prognosis than pSS-PAH, with improved exercise capacity and milder haemodynamic abnormalities. However, overlap with PBC/AIH is associated with a poorer prognosis. These findings highlight the heterogeneity of SS-PAH and the need for tailored treatment based on underlying autoimmune conditions. TRIAL REGISTRATION: ClinicalTrials.gov, https://clinicaltrials.gov, NCT05980728.