Echocardiographic indices and severity of mitral regurgitation in dogs with preclinical degenerative mitral valve disease

BACKGROUND: Describing severity of mitral regurgitation (MR) in dogs with degenerative mitral valve disease (DMVD) is challenging. HYPOTHESIS/OBJECTIVES: Mitral regurgitant fraction (RF), effective regurgitant orifice area (EROA), and the ratio of mitral regurgitant to aortic flow (Q(MR):Q(Ao)) can be calculated from routine echocardiographic measurements and provide additional information regarding MR severity. ANIMALS: Fifty‐seven dogs with preclinical DMVD including 36 without and 21 with cardiomegaly. METHODS: Prospective observational study. The expected relationships among RF, EROA, and Q(MR):Q(Ao) and 1‐dimensional measurements including left atrium to aortic root diameter ratio (LA:Ao) and normalized left ventricular internal dimension at end‐diastole (LVIDdN) were mathematically derived and calculated using echocardiographic data from the study population. Nonlinear goodness of fit was determined by calculation of the root mean standard error. The correlations between 1‐dimensional and multidimensional indices were analyzed using receiver operating characteristic curves. RESULTS: The relationships among RF, EROA, Q(MR):Q(Ao), and both LA:Ao and LVIDdN were curvilinear, and the multidimensional indices differentiated MR of variable severity. By contrast, 1‐dimensional measurements were insensitive to MR severity until RF equaled or exceeded 50%. Regurgitant fraction ≥50%, EROA to body surface area ≥0.347 and Q(MR):Q(Ao) ≥0.79 were strongly associated with LA:Ao ≥1.6 and LVIDdN ≥1.7. CONCLUSIONS AND CLINICAL IMPORTANCE: Regurgitant fraction, EROA, and Q(MR):Q(Ao) quantify MR severity in dogs with preclinical DMVD in a manner that 1‐dimensional measurements do not.