Survival Characteristics and Prognostic Variables of Dogs with Mitral Regurgitation Attributable to Myxomatous Valve Disease

Background: There are few studies evaluating the natural history and prognostic variables in chronic mitral valve disease (CMVI) in a heterogeneous population of dogs. Objectives: To estimate survival and prognostic value of clinical and echocardiographic variables in dogs with CMVI of varying severity. Five hundred and fifty‐eight dogs belonging to 36 breeds were studied. Methods: Dogs were included after clinical examination and echocardiography. Long‐term outcome was assessed by telephone interview with the owner. Results: The mean follow‐up time was 22.7 ± 13.6 months, and the median survival time was 19.5 ± 13.2 months. In univariate analysis, age>8 years, syncope, HR>140 bpm, dyspnea, arrhythmias, class of heart failure (International Small Animal Cardiac Health Council), furosemide therapy, end‐systolic volume‐index (ESV‐I)>30 mL/m2, left atrial to aortic root ratio (LA/Ao)>1.7, E wave transmitral peak velocity (Emax)>1.2 m/s, and bilateral mitral valve leaflet engagement were associated with survival time when all causes of death were included. For the cardiac‐related deaths, all the previous variables except dyspnea and EDV‐I>100 mL/m2 were significantly associated with survival time. Significant variables in multivariate analysis (all causes of death) were syncope, LA/Ao>1.7 m/s, and Emax>1.2 m/s. For cardiac‐related death, the only significant variable was LA/Ao>1.7. Conclusions and Clinical Importance: Mild CMVI is a relatively benign condition in dogs. However, some clinical variables can identify dogs at a higher risk of death; these variables might be useful to identify individuals that need more frequent monitoring or therapeutic intervention.