Mitral Regurgitation Severity and Left Ventricular Systolic Dimension Predict Survival in Young Cavalier King Charles Spaniels

BACKGROUND: Development and progression of myxomatous mitral valve disease (MMVD) in dogs are difficult to predict. Identification at a young age of dogs at high risk of adverse outcome in the future is desirable. HYPOTHESIS/OBJECTIVES: To study the predictive value of selected clinical and echocardiographic characteristics associated with MMVD obtained at a young age for prediction of long‐term cardiac and all‐cause mortality in Cavalier King Charles Spaniels (CKCS). ANIMALS: 1125 privately owned CKCS. METHODS: A retrospective study including CKCS examined at the age of 1–3 years. Long‐term outcome was assessed by telephone interview with owners. The value of variables for predicting mortality was investigated by Cox proportional hazard and Kaplan‐Meier analyses. RESULTS: Presence of moderate to severe mitral regurgitation (MR) (hazard ratio (HR) = 3.03, 95% confidence interval (95% CI) = 1.48–6.23, P = 0.0025) even intermittent moderate to severe MR (HR = 2.23, 95% CI = 1.48–6.23, P = 0.039) on color flow Doppler echocardiography was significantly associated with increased hazard of cardiac death. An interaction between MR and sex was significant for all‐cause mortality (P = 0.035), showing that males with moderate to severe MR had a higher all‐cause mortality compared to males with no MR (HR = 2.38, 95% CI = 1.27–4.49, P = 0.0071), whereas no difference was found between female MR groups. The risk of cardiac (HR = 1.37, 95% CI = 1.14–1.63, P < 0.001) and all‐cause (HR = 1.13, 95% CI = 1.02–1.24, P = 0.016) mortality increased with increasing left ventricular end‐systolic internal dimension normalized for body weight (LVIDS(N)). CONCLUSIONS AND CLINICAL IMPORTANCE: Moderate to severe MR, even if intermittent, and increased LVIDS(N) in dogs <3 years of age were associated with cardiac death later in life in CKCS.