Preventive effect of sildenafil on right ventricular function in rats with monocrotaline-induced pulmonary arterial hypertension

The present study aimed to evaluate the preventive effect of sildenafil treatment on pulmonary hypertension (PH) induced by monocrotaline (MCT) in rats. Fifty-four 12-week-old male Sprague-Dawley rats were injected with MCT or saline solution (MCT-injected rats: n=36; saline: n=18). Serial echocardiography and right ventricular systolic pressure (RVSP) measurements via a cardiac catheter were performed at 2, 4 and 6 weeks after the injection. After injection of MCT, rats received oral sildenafil (MCT/sildenafil group: n=18) or no treatment (MCT group: n=18) until undergoing echocardiography and cardiac catheterization. RVSP in the MCT/sildenafil group was lower than that in the MCT group at 4 (P<0.001) and 6 weeks (P<0.001). The septal curvature was improved in the MCT/sildenafil group compared with the MCT group. This finding showed that sildenafil prevented flattening of the interventricular septum because of right ventricular pressure overload. The ratio of peak trans-tricuspid early diastolic wave velocity to active filling with atrial systolic velocity showed that sildenafil improved diastolic function. Tricuspid annular plane systolic excursion and tricuspid annular systolic velocity in the MCT/sildenafil group did not show preserved myocardial contraction after administration of sildenafil. Administration of sildenafil leads to a reduction in RVSP and improvement in cardiac function in rats with PH induced by MCT. The vasodilatory action of sildenafil improves right ventricular diastolic function, but the intrinsic, positive, inotropic effect of sildenafil is minimal.