Effects of Riociguat on Right Ventricular Remodelling in Chronic Thromboembolic Pulmonary Hypertension Patients: A Prospective Study.

Background: The effects of riociguat treatment on right ventricular (RV) metabolism, perfusion, and output in patients with chronic thromboembolic pulmonary hypertension (CTEPH) are unknown. In this study, RV changes associated with riociguat therapy were investigated.

Methods: Six patients with CTEPH received riociguat for 6 months. Right heart catheterization (only baseline), cardiac magnetic resonance imaging, and positron emission tomography using tracers for myocardial glucose uptake (F-fluorodeoxyglucose [F-FDG]) and perfusion (N-ammonia) were performed at baseline and follow-up time points.

Results: At baseline, median RV ejection fraction (RVEF) was 47% (22%-53%) with a mean pulmonary artery pressure (PAP) of 42 mm Hg (27-57 mmHg). Two patients were New York Heart Association functional class III and the rest were class II. Baseline RV F-FDG uptake was inversely correlated with RVEF (r = -0.82; P = 0.04) and positively correlated with mean PAP (r = 0.94; P = 0.004). Riociguat treatment was associated with a significant increase in RV stroke volume index by 13.5 mL/m (6.8-17.5 mL/m; P = 0.03) and a trend of improved RVEF by 5% (1%-9%; P = 0.09). Myocardial fibrosis indicated by the volume of myocardium exhibiting late gadolinium enhancement was reduced by 4.4 mL (0.2-5.2 mL; P = 0.09). F-FDG (metabolism) and N-ammonia (perfusion) positron emission tomography did not show a significant difference over the follow-up period. The studied patients (except for 1) had a reduction in the ratio of RV F-FDG uptake to RV perfusion, suggesting improved RV metabolism-flow relationships.

Conclusions: Riociguat treatment was associated with increased RV stroke volume index and trends for improvement in myocardial remodelling in patients with CTEPH. A larger clinical study is warranted to observe the therapeutic benefits of riociguat on RV remodelling.