Body Weight- and Age-Adjusted Reference Model for Septal Mitral Annular Plane Systolic Excursion in Healthy Dogs

Mitral annular plane systolic excursion (MAPSE) is an M-mode index of left ventricular longitudinal systolic motion.In dogs, interpretation of raw MAPSE is affected by wide body size variation; and the independent effect of age after body weight adjustment has not been quantified.This study aimed to develop a body weight-and age-adjusted reference model for septal MAPSE and derive normalized indices.This two-center retrospective study included 180 client-owned healthy dogs examined between November 2016 and December 2023.Inclusion criteria included the absence of structural cardiac abnormalities, sinus rhythm, systolic blood pressure <140mmHg, and no clinically relevant thoracic radiographic, hematologic, or biochemical abnormalities.Septal MAPSE was measured by M-mode echocardiography from the apical four-chamber view and averaged over three cycles.Multiple linear regression modeled log₁₀(MAPSE), using log₁₀(body weight) and age.Heart rate and sex/neuter status were assessed as additional covariates, and study center was assessed for systematic center-related differences.Model-based Z-scores and percentage of predicted MAPSE values were calculated.The final model was log₁₀(MAPSE)=0.6279+0.3243×log₁₀(BW)-0.008767×age,explaining 70.2% of variation in log₁₀(MAPSE).Body weight and age were significant predictors (P<0.0001).Predicted MAPSE scaled allometrically with body weight and decreased by 2.0% per year.Z-scores and percentage of predicted MAPSE showed no residual association with body weight or age.Septal MAPSE in healthy dogs is body weightand age-dependent.This model provides body weight-and age-adjusted expected values for interpreting septal MAPSE within the range represented by this cohort.