Abstract Body (Do not enter title and authors here): Background. According to the European Guidelines, “low-risk” pulmonary arterial hypertension (PAH) patients is defined as a risk of death < 5% within a year and represents a treatment-goal. However, the impact of morbidity (e.g. hospitalization and clinical worsening), were not included in this definition.

Research Questions. Can REVEAL 2.0 risk score further identify low-risk PAH patients for both morbidity and mortality?

Aims. Using the REVEAL 2.0 risk score, to propose a modified definition of “low-risk” to include the risk of both morbidity and mortality at 1- and 3-years, respectively.

Methods. A harmonized dataset from 8 PAH randomized controlled trials from the FDA was used for this analysis and REVEAL 2.0 risk score was calculated for each patient. Modified low-risk was a priori defined by “risk of death ≤ 5% at 3-years and risk of clinical worsening ≤10% at 1-year”. Clinical worsening was defined as any of the following: lung transplantation or hospitalization due to PAH worsening, initiation of prostanoids/chronic oxygen, 15% decrease in 6-MWD from baseline, a worsening of NYHA, addition of a new PAH medication.

Results. A total of 4,122 PAH patients were included: median age 49 (36, 62) yo, mPAP 50 (40, 60) mmHg, PVR 10 (7, 14) WU, 6MWD 375 (306, 423) m, NTproBNP 884 (230, 3010) pg/mL. Patients with a REVEAL 2.0 risk score ≤ 4 had a 1-year clinical worsening free-survival and 3-year survival rate of 92% and 95% (Figure 1). The 3-years survival was significantly better in patients with a REVEAL 2.0 ≤ 4 compared to 5-6: HR=0.47, 95%CI[0.27-0.84], p=0.01. Compared to patients with REVEAL 2.0 risk score of 5-6 (“classical” low-risk), those with a REVEAL 2.0 risk score ≤ 4 (“refined low-risk”) had a better clinical, biological, hemodynamic presentation, and outcomes (Table 1).

Conclusion. This study is the first embedding both morbidity and mortality within the definition of low risk for PAH patients and suggests that PAH patients with REVEAL 2.0 risk score ≤ 4 meet this definition. This definition may be a promising new treatment-goal strategy in future randomized controlled trials but also for daily clinical practice.