Effect of riociguat on pulmonary arterial compliance in the PATENT and CHEST studies

Pulmonary arterial compliance is a measure of the pulsatile afterload of the right ventricle. Lower pulmonary arterial compliance is associated with reduced right ventricular function and worse prognosis in pulmonary hypertension. The effect of pulmonary vasodilators on pulmonary arterial compliance has not been evaluated in detail in pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension. In this post hoc analysis of patients with pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension in the PATENT and CHEST studies, we evaluated the change in pulmonary arterial compliance with riociguat versus placebo. Association of pulmonary arterial compliance with clinical outcomes was assessed using Kaplan–Meier and Cox proportional hazards analyses. Compared with placebo, riociguat significantly improved pulmonary arterial compliance in patients with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension. Pulmonary arterial compliance at baseline was associated with survival and clinical worsening-free survival in pulmonary arterial hypertension but only with clinical worsening-free survival in chronic thromboembolic pulmonary hypertension. In patients with pulmonary arterial hypertension, pulmonary arterial compliance at follow-up ≥1.6 mL/mmHg was associated with better outcomes than pulmonary arterial compliance <1.6 mL/mmHg. In patients with chronic thromboembolic pulmonary hypertension, pulmonary arterial compliance at follow-up did not predict outcomes. Cox proportional hazards analyses showed no association between change in pulmonary arterial compliance and outcomes in patients with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension. In conclusion, riociguat improved pulmonary arterial compliance in patients with pulmonary arterial hypertension or chronic thromboembolic pulmonary hypertension. Pulmonary arterial compliance at baseline or follow-up, rather than change in pulmonary arterial compliance, is of prognostic importance for outcomes.