Abstract: Pulmonary hypertension is a complex syndrome that affects pulmonary circulation and the right heart. This syndrome progression is a prognosis-worsening factor and is associated with decreased survival and low quality of living. Conventional treatment includes phosphodiesterase 5 inhibitors (sildenafil or tadalafil) and combined drugs such as pimobendan (phosphodiesterase 3 inhibitor). In the terminal stages, this treatment could be insufficient and cannot control all the symptoms. In this study, we retrospectively analyzed patients with severe pulmonary hypertension and additional treatment with bosentan (endothelin-1 inhibitor) which is believed to improve prognosis and outcome in diseased dogs. We studied 23 client-owned dogs with refractory pulmonary hypertension of different etiology, already treated with sildenafil and with symptoms of dyspnea, syncope, ascites, and weakness. The diagnosis was based on the EchoCG studies and disease history analysis, according to ACVIM consensus statements in pulmonary hypertension. In order to determine the efficacy of bosentan, based on its extended impact and laboratory data in animals, we divided patients into two groups: 1 - dogs treated for less than two weeks (n=9): 2 - dogs treated for a longer period (n=14).
Results: 2nd group had significant improvements in ascites (9/14), dyspnea (14/14), syncope (13/14), activity (10/14). Median survival time in the 1st group was 5 days, in the 2nd - 5 months. EchoCG showed a positive trend in TAPSE, pulmonary vein to right pulmonary artery ratio, and right pulmonary artery distensibility index, with a decrease in RV diameter and tricuspid regurgitation velocity after two weeks of treatment. Conclusion. These findings show significant improvement in clinical and EchoCG parameters after bosentan treatment compared to previous sildenafil medication
