Sessions

Myxomatous mitral valve disease (MMVD) is the most common acquired cardiac disease in dogs. Its clinical significance stems not only from its high prevalence but also from its highly variable course among individual dogs: some remain asymptomatic throughout their lives, whereas in others, the disease progresses to congestive heart failure. Therefore, prognostic parameters that provide information on the expected outcome at the time of diagnosis are of particular importance.

The aim of our study was to determine the extent to which parameters obtained at the initial echocardiographic examination predict all-cause and cardiac-related death, and whether these parameters can also be applied within individual ACVIM stages. We retrospectively analysed data from 141 dogs with MMVD examined at the Small Animal Clinic of the University of Veterinary Medicine Budapest using Kaplan–Meier analysis and Cox regression (median follow-up, 26.7 months; 59 deaths, including 28 cardiac deaths).

In the entire cohort, the strongest predictors of cardiac-related death were normalized left atrial measurements. Among these, LAD normalized to body weight (LADn) retained prognostic value independently of ACVIM stage (HR=1.153; 95% CI: 1.041–1.276; p=0.006).

The subgroup analysis revealed two clinically important findings. In preclinical (B1–B2) dogs, all-cause death was predicted exclusively by age, whereas cardiac-related death was predicted exclusively by left atrial indices; the strongest discrimination was achieved with a LAmax/Ao cut-off of ≥2.50 (HR=7.08; permutation-adjusted p=0.011). However, survival did not differ significantly between dogs in ACVIM stages B1 and B2 (all-cause death: p=0.477; cardiac-related death: p=0.591), and the defining criteria for stage B2 (LA/Ao ≥1.6; LVIDDn ≥1.7) did not discriminate risk within the asymptomatic stage. In the symptomatic (C/D) group, the cut-offs used in the preclinical stage were not applicable, as most dogs were already above these thresholds; consequently, a ceiling effect resulted in a loss of discriminatory ability. Therefore, cut-offs should be adapted to the respective disease stage and the population under investigation.

Overall, continuous, body-size-normalized left atrial measurements provided more accurate risk stratification than the ACVIM stage alone, especially in asymptomatic animals.