Initial treatment strategies and outcomes across haemodynamic thresholds and risk stratification in incident systemic sclerosis–associated pulmonary arterial hypertension: a EUSTAR analysis

OBJECTIVE: Real-world initial treatment strategies in SSc-PAH remain incompletely described. We aimed to characterise these strategies across haemodynamic thresholds and risk strata and evaluate outcome associations. METHODS: We analysed treatment-naïve SSc-PAH patients in EUSTAR (2000-2021) fulfilling the 2022 haemodynamic definition. Initial therapy comprised treatment initiated within 4 months of RHC. As-treated (AT) analyses were primary and intention-to-treat (ITT) analyses supportive. Outcomes were all-cause mortality and 36-month PAH progression. RESULTS: Among 301 patients, 198 (66%) initiated therapy and 170 maintained therapy for ≥3 months. Therapy was initiated in 31% with milder haemodynamic impairment (mPAP 21-24 mmHg and/or PVR 2-3 WU) versus 79% fulfilling the previous haemodynamic definition; combination therapy increased from 14% to 67% across low- to high-risk strata. Over a median 3.9 years, 125 (42%) died and 85/227 (37%) progressed. Adjusted ITT analyses showed no association with either outcome, whereas adjusted AT analyses showed lower mortality risk with sustained monotherapy and combination therapy (HR 0.50, 95% CI 0.27-0.92 and HR 0.40, 95% CI 0.18-0.88, respectively) and lower PAH progression risk with sustained initial therapy (HR 0.37, 95% CI 0.18-0.76). In the milder haemodynamic subgroup, the mortality estimate was directionally consistent but imprecise. CONCLUSION: Initial treatment strategies reflected haemodynamic severity and baseline risk, while variation suggested potential implementation gaps. Sustained initial therapy was associated with lower risks of mortality and PAH progression. Contrasting ITT and AT estimates highlight challenges in observational treatment-outcome comparisons. Findings in the milder haemodynamic subgroup support dedicated prospective studies.