Quantitative mitral regurgitation and conventional echocardiographic variables in canine myxomatous mitral valve disease.

Introduction: Disease severity in dogs with myxomatous mitral valve disease (MMVD) is commonly assessed using conventional echocardiographic variables and staging systems based on cardiac remodeling and heart failure status. Multiparametric scoring systems incorporating variables such as early diastolic transmitral velocity (E-wave) have also been recently proposed. However, these approaches primarily reflect secondary morphological and loading changes rather than directly quantifying severity of mitral regurgitation (MR). Therefore, quantitative regurgitant indices may provide additional information regarding the functional severity of MR. Methods: This retrospective study included 167 predominantly small-breed dogs with MMVD evaluated at Japanese referral centers, classified according to the American College of Veterinary Internal Medicine (ACVIM) staging system. Body weight-normalized regurgitant volume (RVol/kg) and regurgitant fraction (RF) were calculated using volumetric methods. Group comparisons among ACVIM stages, correlation analysis, logistic regression analysis, and receiver operating characteristic analysis were performed to evaluate associations between regurgitant indices and conventional echocardiographic variables. Results: RVol/kg and RF increased significantly with advancing disease stage (both Discussion: Quantitative regurgitant indices were associated with conventional echocardiographic variables and may provide complementary information regarding MR severity in dogs with MMVD. In this predominantly small-breed Japanese MMVD population, the mitral-aortic VTI ratio showed strong associations with quantitative regurgitant indices and may be a clinically useful Doppler-derived surrogate for MR severity, although prospective studies are required to confirm these findings.