Short term effects of sildenafil in treatment of pulmonary hypertension in degenerative mitral valve disease dogs

Degenerative mitral valve disease (DMVD) is the most common acquired cardiac disease in small breed dogs. Pulmonary hypertension (PH) is a common complication in DMVD that can worsen the clinical signs, cardiac function, and median survival time of DMVD dogs. Conventional therapy of DMVD can reduce systolic pulmonary arterial pressure (sPAP) minimally. Thus, additional therapy is required. Sildenafil is used to treatment of PH in various causes, but the effect of sildenafil in the treatment of PH secondary to DMVD is not published yet. Therefore, this study aimed to evaluate the effects of sildenafil in combination with conventional therapy in PH dogs caused by DMVD. Fourteen dogs were diagnosed with PH secondary to DMVD stage C and were being on conventional therapy. The recruited dogs were randomly assigned to the placebo (n=7) and sildenafil (n=7) groups. At day 0, the recruited dogs were performed a physical examination, clinical scores assessment, electrocardiography (ECG) measurement, systolic blood pressure measurement (SBP), blood collection, thoracic radiography examination, and echocardiography examination for baseline. Dogs in the sildenafil group received a combination of conventional therapy and sildenafil. The median dose of sildenafil was 1.79 (1.69-2.19) mg/kg every 8 hours for 1 week, while the placebo group received a placebo with the same regimen. At day 7, the recruited dogs were performed all examinations same as day 0. The results showed that the sildenafil group had a significant decrease in sPAP (p=0.043), while the sPAP did not change in the placebo group. However, clinical and lung scores did not improve after treatment with sildenafil. Additionally, this study found that sPAP had a positive correlation with heart rate and isovolumetric contraction time of right ventricle (p=0.005 and 0.014, respectively). In conclusion, sildenafil had a synergist effect to conventional therapy in reducing sPAP but effects of sildenafil on clinical and lung scores were not found.