SGCB and pulmonary arterial hypertension: In PAH patients, while acute treatment with the phosphodiesterase (PDE)5 inhibitor Sildenafil improved RV diastolic function (55), recent trials in non-PAH heart failure patients with Sildenafil or the soluble guanylate cyclase (sGC) stimulator Riociguat failed to meet their primary clinical endpoints (56, 57).