Echocardiographic predictors of persistent left heart enlargement in dogs undergoing surgical mitral valve repair

INTRODUCTION/OBJECTIVES: Mitral valve repair (MVR) under cardiopulmonary bypass is an established procedure associated with prolonged survival in dogs with myxomatous mitral valve disease compared to medical management alone. This study aimed (1) to assess the degree and timescale of left heart reverse remodeling in dogs undergoing MVR and (2) to identify demographic and perioperative echocardiographic variables predictive of persistent left heart enlargement after MVR. ANIMALS, MATERIALS AND METHODS: This was a retrospective longitudinal observational study including 66 dogs undergoing MVR at a single center with ≥12 months' follow-up. The degree and time course of left heart reverse remodeling were assessed. Logistic regression analyses were performed to identify demographic and echocardiographic predictors of persistent left heart enlargement after MVR. RESULTS: Decreased left atrial (left atrial-to-aortic root ratio: 2.36 [interquartile range: 1.96-2.87] vs. 1.56 [1.4-1.78], P<0.001) and left ventricular (left ventricular internal diameter in diastole normalized for body weight [LVIDdN]: 2.14 [1.93-2.37] vs. 1.65 [1.47-1.81], P<0.001) dimensions were observed within three months after MVR, with minimal reduction thereafter. Greater baseline LVIDdN (P<0.001) and heavier body weight (P=0.002) were predictive of persistent left heart enlargement. STUDY LIMITATIONS: This was a retrospective study, with a small number of dogs included. Echocardiographic assessment was performed by multiple operators with variable follow-up periods. CONCLUSIONS: This study suggests that reverse remodeling predominantly occurs within the first three months after MVR, and persistent left heart enlargement may be expected in dogs with greater baseline LVIDdN and heavier body weight.