Key result
Pimobendan reduced mitral regurgitant fraction by a mean of 9.8% in dogs with myxomatous mitral valve disease by augmenting systolic contraction of the mitral annulus.
Why the study?
Pimobendan might affect mitral annular dynamics in dogs with myxomatous mitral valve disease, but its short-term effects on mitral annular dynamics, mitral regurgitation severity, and systemic arterial compliance required investigation.
Does oral pimobendan improve mitral annular dynamics and reduce mitral regurgitation severity in dogs with myxomatous mitral valve disease?
Does oral pimobendan improve mitral annular dynamics and reduce mitral regurgitation severity in dogs with myxomatous mitral valve disease?
Short-term pimobendan administration decreases mitral regurgitation severity by augmenting systolic contraction of the mitral annulus in dogs with myxomatous mitral valve disease.
Hypothesis-generating for pimobendan effects on MAD in stage B2 MMVD; RCTs needed before assessing MR or outcome impact.
Background Pimobendan might affect mitral annular dynamics (MAD) in dogs with myxomatous mitral valve disease (MMVD); in humans, alterations in MAD are known to increase the severity of mitral regurgitation (MR). Hypothesis/Objectives To investigate the short-term effect of pimobendan on MAD, severity of MR, and systemic arterial compliance in dogs with MMVD. Animals Twenty dogs with newly diagnosed ACVIM stage B2 MMVD. Methods Prospective, open-label, longitudinal study. All dogs underwent echocardiographic and cardiac computed tomographic (CCT) examinations before and 2 weeks after oral administration of pimobendan. Changes in MAD, leaflet-to-annulus index, left heart volumes, regurgitant volume/fraction, and aortic distensibility index were evaluated on CCT. Results All dogs completed the study without major adverse events. Pimobendan decreased normalized end-systolic mitral annular area (mean difference of 1.38 cm2/m2; 95% CI, 0.79-1.97 cm2/m2; P < .001), aortoparietal distance (mean difference of 1.03 mm/kg1/3; 95% CI, 0.54-1.53 mm/kg1/3; P < .001), and intercommissural distance (mean difference of 0.75 mm/kg1/3; 95% CI, 0.44-1.06 mm/kg1/3; P < .001). Mean leaflet-to-annulus index increased (mean difference of 0.06; 95% CI, 0.02-0.09; P = .002). Changes in left ventricular end-diastolic and end-systolic volumes, left atrial end-diastolic and end-systolic volumes, regurgitant volume (mean reduction of 0.31 mL/kg; 95% CI, 0.13-0.5 mL/kg), and regurgitant fraction (mean reduction of 9.8%; 95% CI, 5.2%-14.3%) were detected (all P < .05) with administration of pimobendan. There was no detectable difference in aortic distensibility index (P = .6). Conclusions and clinical importance Short-term pimobendan administration decreases MR severity by augmenting systolic contraction of the mitral annulus. The study provides new insight into the mechanism of action of pimobendan in dogs with MMVD.
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Chi et al. (2026) studied this question. Pimobendan reduced mitral regurgitant fraction by a mean of 9.8% in dogs with myxomatous mitral valve disease by augmenting systolic contraction of the mitral annulus.
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