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Simple Summary: Pulmonary hypertension is a fatal comorbidity in dogs with left-sided heart disease. Various oral pulmonary vasodilators have been effective in treating canine pulmonary hypertension; however, no studies have compared their hemodynamic effects. This study compared the hemodynamic effects of selected pulmonary vasodilators (15 µg/kg beraprost, 1.0 mg/kg sildenafil, and their combination) in canine models of mitral regurgitation (the most common cardiac disease in dogs). Significant improvements in pulmonary hypertension were observed with all study drugs. Pulmonary vasodilating effects differed among the study's drugs. Sildenafil showed a more potent pulmonary vasodilating effect than beraprost; however, sildenafil significantly worsened the left-heart loading condition. Although beraprost showed a weaker pulmonary vasodilating effect than sildenafil, no significant worsening in the left-heart loading condition was observed. Combination therapy resulted in the strongest pulmonary and systemic vasodilating effects without worsening the left-heart loading condition. This study demonstrated the differences between beraprost and sildenafil in pulmonary and systemic vasodilating effects. Sildenafil involved the risk of worsening the left-heart load, although it was effective in treating pulmonary hypertension. Combination therapy with beraprost and sildenafil synergistically dilated the pulmonary and systemic vessels, indicating a more potent treatment option. Previous reports have shown that various oral pulmonary vasodilators are effective against canine pulmonary hypertension (PH). However, no studies have compared their hemodynamic effects. We aimed to compare the hemodynamic effects of 15 µg/kg beraprost sodium, 1.0 mg/kg sildenafil, and their combination, in dogs with experimentally induced mitral regurgitation. This experimental crossover study evaluated the hemodynamic and functional effects of oral pulmonary vasodilators by application of right-sided heart catheterization and echocardiography. Beraprost significantly decreased pulmonary and systemic vascular resistance. Additionally, beraprost increased right-ventricular stroke volume and left-ventricular cardiac output without worsening left-heart size and left-atrial pressure. The pulmonary vasodilatory effects of sildenafil were stronger, and its systemic vasodilatory effects were weaker than those of beraprost. However, sildenafil significantly increased the left-ventricular volume, left-atrial pressure indicator, and right-ventricular cardiac output. Combination therapy resulted in the strongest pulmonary and systemic vasodilating effects without worsening the left-heart size and left-atrial pressure indicators. Both beraprost and sildenafil were effective against canine PH; however, sildenafil was associated with the risk of worsening left-heart loading. Combination therapy with beraprost and sildenafil synergistically dilated pulmonary and systemic vessels, indicating a more potent treatment option for severe PH cases. [ABSTRACT FROM AUTHOR]

Background: Progression to combined post‐ and pre‐capillary pulmonary hypertension (PH) provides prognostic information in human patients with post‐capillary PH. Pulmonary vascular resistance estimated by echocardiography (PVRecho) is useful for the stratification of dogs with myxomatous mitral valve disease (MMVD) and detectable tricuspid regurgitation. Objectives: To evaluate the prognostic value of PVRecho in dogs with MMVD. Animals: Fifty‐four dogs with MMVD and detectable tricuspid regurgitation. Methods: Prospective cohort study. All dogs underwent echocardiography. The PVRecho was calculated based on tricuspid regurgitation and the velocity‐time integral of the pulmonary artery flow. To evaluate the influence of echocardiographic variables on cardiac‐related deaths, Cox proportional hazard analysis was performed. Additionally, Kaplan‐Meier curves classified by PVRecho tertiles were made and compared using log‐rank tests to evaluate the influence of PVRecho on all‐cause mortality and cardiac‐related death. Results: The median follow‐up time was 579 days. Forty‐one dogs with MMVD (PH severity [number]: no or mild, 21/33; moderate, 11/11; severe, 9/10) died during the study. In the multivariable Cox proportional hazard analysis adjusted for age, sildenafil administration, and American College of Veterinary Internal Medicine stage of MMVD, left atrial to aortic diameter ratio and PVRecho remained significant (adjusted hazard ratio [95% confidence interval]: 1.2 [1.1‐1.3] and 2.1 [1.6‐3.0], respectively). Higher PVRecho showed a significant association with lower survival rates. Conclusions and Clinical Importance: Left atrial enlargement and high PVRecho were independent prognostic factors in dogs with MMVD and detectable tricuspid regurgitation. [ABSTRACT FROM AUTHOR]