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.