Effect of Pimobendan on Echocardiographic Values in Dogs with Asymptomatic Mitral Valve Disease

Background: Pimobendan (PIMO) is a novel inodilator that has shown promising results in the treatment of advanced mitral valve disease (MVD), but little is known about its hemodynamic effects, especially regarding the mitral regurgitant volume in naturally occurring MVD. Hypothesis: The addition of pimobendan to treatment decreases the regurgitant fraction (RF) in dogs with asymptomatic MVD. Animals: Twenty-four client-owned dogs affected by International Small Animal Cardiac Health Council class Ib MVD. Methods: Prospective, blinded, and controlled clinical trial. Dogs were assigned to a PIMO treatment group (n 5 19) (0.2–0.3mg/kg q12h) or a control group (n5 5). Echocardiographic evaluations were performed over a 6-month period. Results: The addition of PIMO to treatment did not decrease the RF of dogs affected by asymptomatic class 1b MVD over the study period (P 5.85). There was a significant increase in the ejection fraction of the PIMO treated dogs at 30 days (80.8 1.42 versus 69.0 2.76, corrected P 5.0064), and a decrease in systolic left ventricular diameter (corrected P 5.011) within the PIMO group compared with baseline. However, this improvement in systolic function was not sustained over the 6-month trial period. Conclusion and Clinical Importance: This study did not identify beneficial long-term changes in the severity of mitral regur-gitation after addition of PIMO to angiotensin converting enzyme inhibitor treatment of dogs with asymptomatic MVD