To evaluate vena contracta and other echocardiographic measures of myxomatous mitral valve disease (MMVD) severity in a multivariable analysis of survival in dogs.

70 dogs diagnosed with MMVD from stored echocardiographic images that met study inclusion criteria.

Left heart dimensions were measured as well as mitral regurgitant jet area/left atrial area (JAR), early mitral filling velocity (E_vel), extent of mitral valve prolapse in right and left views (Prol_R, Prol_L), Prol indexed to aortic diameter (Prol_R:Ao, Prol_L:Ao), presence of a flail leaflet (Flail_R, Flail_L), and mitral regurgitation vena contracta diameter (VC_R, VC_L) indexed to aortic diameter (VC_R:Ao, VC_L:Ao). Follow-up from referring veterinarians was obtained by questionnaire or telephone to determine survival times. Inter- and intra-observer agreement was evaluated with Bland–Altman plots and weighted Kappa analysis. Survival was analyzed using Kaplan–Meier curves, logrank tests and Cox's proportional hazards.

Logrank analysis showed VC_L:Ao, VC_R:Ao, Flail_L, Prol_R:Ao, Prol_L:Ao, left ventricular internal dimension in diastole indexed to aortic diameter (LVIDD:Ao) >2.87, left atrium to aorta ratio (LA/Ao) >1.6, and E_vel >1.4 m/s were predictors of cardiac mortality. In a multivariable analysis, the independent predictors of cardiac mortality were E_vel >1.4 m/s [hazard ratio (HR) 5.0, 95% confidence interval (CI) 2.5–10.3], Flail_L (HR 3.1, 95% CI 1.3–7.9), and Prol_R:Ao (HR 2.8, 95% CI 1.3–6.3).

Echocardiographic measures of mitral regurgitation severity and mitral valve pathology provide valuable prognostic information independent of chamber enlargement in dogs with MMVD.