Clinical Significance of Guanylate Cyclase Stimulator, Riociguat, on Right Ventricular Functional Improvement in Patients with Pulmonary Hypertension

Background: Riociguat is a soluble guanylate cyclase stimulator that improves hemodynamics in patients with pulmonary hypertension (PH). Accumulating evidence implicates the additional effect of riociguat on the increase in cardiac output. However, its mechanisms have not been fully understood. This study aimed to investigate whether riociguat could ameliorate right ventricular (RV) contraction as well as hemodynamics. Methods: We studied 45 patients with pulmonary arterial hypertension (14) or chronic thromboembolic pulmonary hypertension (31) and evaluated hemodynamics, using right-sided heart catheterization, before and after the administration of riociguat. RV function was assessed by echocardiography, including speckle-Tracking echocardiography. Results: Riociguat significantly improved the WHO functional class and reduced the mean pulmonary arterial pressure and vascular resistance. In addition, the cardiac index increased. RV remodeling was ameliorated after riociguat administration as assessed by the echocardiographic parameters, such as RV diameter and RV area index. RV function, including RV fractional area change and RV global longitudinal strain, also significantly improved, and their improvement was even observed in patients with mild PH after pulmonary endarterectomy or balloon pulmonary angioplasty. Furthermore, covariance analysis revealed that RV global longitudinal strain and RV fractional area change improved after riociguat administration, even with the same mean pulmonary arterial pressure, implicating the improvement of RV contractile function by riociguat, regardless of RV loading. Conclusions: Riociguat not only improved the hemodynamics of patients with PH but also ameliorated the echocardiographic parameters with RV function. RV strain could detect the subtle improvement in mild PH, and riociguat may have a benefit even after intervention, as assessed by speckle-Tracking echocardiography.