Survival Characteristics and Prognostic Variables of Dogs with Preclinical Chronic Degenerative Mitral Valve Disease Attributable to Myxomatous Degeneration

Background Preclinical myxomatous mitral valve degeneration ( MMVD ) includes a heterogeneous group of dogs. Therefore, identifying risk factors for progression of the disease is of clinical importance. Objectives To investigate survival time and risk factors for clinical and echocardiographic variables taken at initial examination for clinical progression in preclinical MMVD dogs. Animals A total of 256 dogs with stage B1 or B2 MMVD. Materials and Methods Medical records of 256 dogs with preclinical MMVD were reviewed retrospectively. Long‐term outcome was assessed by telephone interview. Dogs alive at the time of phone interview were asked to return to the hospital for re‐evaluation of their cardiac status. Results Seventy of 256 (27.3%) dogs died during the observation period. The median survival time, regardless of cause of death, was 588 (range 75–1,668) days. The presence of a murmur was associated with an increased risk of death ( AHR 2.14; 95% CI 1.12, 4.11; P  = 0.022). Thirty (12%) deaths were considered cardiac related. LA /Ao > 1.4 was the only negative predictor ( AHR 2.64; 1.13, 6.13; P  = 0.024) for cardiac‐related deaths. Eighty‐three dogs were re‐examined, of which 34 progressed to a more advanced stage of MMVD . The presence of Emax > 1.2 ( AHR 2.75; 95% CI 1.01, 7.48; P  = 0.047) and cough ( AHR 7.89; 95% CI 3.18, 20.07; P  < 0.001) were significant in the multivariate analysis. Conclusions and Clinical Importance Preclinical MMVD represents a relatively benign condition in dogs. Clinicians might find stratification of this dog population according to risk factors based on clinical and echocardiographic findings helpful in determining treatment.