OBJECTIVES: To compare the effects of macitentan on length of stay (LOS), and cost savings due to averted pulmonary arterial hypertension-related hospitalizations stratified by insurance type, commercial or Medicare, using a decision tree model. METHODS: Published references informed the incidence and prevalence of PAH. Published SERAPHIN clinical trial data informed PAH-related hospitalization and mortality rates for placebo. The inputted reduction in hospitalizations was 50% for the macitentan-treated group which is the same for those over and under 65 years of age. Costs for PAH treatments (macitentan, and background therapies sildenafil and iloprost) were inputted from Medispan 2016. Reimbursement costs for hospitalization were calculated by averaging the costs for an initial hospitalization and readmission. For the commercial cohort, the averaged reimbursement cost was $53,679, and for the Medicare cohort, $18,994. Average LOS in days was 14.2 for commercial versus 16.7 for Medicare. Both the mean reimbursement costs and mean LOS were obtained from a published analysis of claims data. Total length of stay includes averted hospitalizations and reductions in the LOS. The model base-case analysis assumes constant mortality rate (2.6%) for the placebo arm. RESULTS: In a commercial plan of 20 million-covered lives, 1,473 PAH cases would be eligible for treatment with macitentan, leading to 143 (50% reduction) fewer hospitalizations/year, $7,694,706 in hospital-related savings, and 3,107 days (76% reduction) in total LOS. In a Medicare plan of 20 million covered lives, 1,386 PAH cases would be eligible for treatment with macitentan, leading to 135 (50% reduction) fewer hospitalizations/year, $2,561,392 in hospital-related savings, and 3,437 days (76% reduction) in total LOS. CONCLUSIONS: Both hypothetical cohorts experienced a reduction in total number and cost of hospitalizations, and length of stay. Due to differences in reimbursement, the commercial group experienced greater hospital-related savings. Further analyses will qualify the effect of macitentan on these outcomes.