Right ventricular contractile reserve and pulmonary arterial compliance differentiate PAH patients with long-term survival and therapeutic success

Introduction: The factors that differentiate long term (>10 year) therapeutic success relative to poor prognosis (<2 years) in pulmonary arterial hypertension (PAH) are not known. The objective was to identify parameters of resting RV function and RV contractile reserve that can differentiate short-term survivors (ST) from long-term survivors (>10 years) (LT). Methods: PAH patients with <2 years of survival (n=6) (ST) on treprostinil therapy compared to patients with >10 years survival (n=7), (LT) were included in the study. All patients underwent a submaximal invasive cardiopulmonary exercise testing. We determined parameters of resting systolic RV contractile function (Ees), RV afterload (Ea), RV-PA coupling (Ees/Ea), diastolic ventricular stiffness (β, beta), PA compliance (Ca), and). RV contractile reserve was defined as the difference between maximal and resting systoic PA pressure. Results: Short-term survivors have increased RA pressure, mean PAP and pulmonary vascular resistance compared to long-term survivors (p<0.05). There are no significant differences in cardiac output or stroke volume but PA compliance is significantly decreased (2.1±0.6 vs 4.7±1.2, p<0.05). RV-PA coupling is not significant different but ST had increased arterial afterload (1.4±0.5 vs 0.6±0.2). Resting RV stroke work was not different but when exercised, LT reached a higher workload, heart rate and RV contractile reserve (30±10 vs 12±5, p<0.05) compared to the ST cohort. Conclusions: RV contractile reserve and PA compliance differentiates long-term survivors (>10 years of treatment) from short-term survivors (<2 years of treatment) on PAH specific therapy.