Diagnostic value of peak transmitral flow velocity for left atrial enlargement in dogs with myxomatous mitral valve disease

Objective: To investigate factors influencing pulsed-wave Doppler transmitral flow profiles and evaluate their diagnostic value in dogs with myxomatous mitral valve disease (MMVD). Methods: Dogs with MMVD underwent echocardiography; thoracic radiography; blood analysis, including N-terminal pro-B-type natriuretic peptide; and clinical staging. Dogs were divided into mitral E/A peak (E/A) reversal and no reversal groups. Correlations of E-wave velocity (E-vel) and peak velocity (P-vel; higher of E or A wave) with MMVD indices were analyzed, and receiver operating characteristic curves assessed diagnostic performance. Results: Of 61 dogs, 25 dogs were assigned to the no reversal group and 36 to the reversal group. No significant differences were identified between the groups in most variables. E-wave velocity correlated strongly with left ventricular dilation indices (vertebral heart size, left ventricular end-diastolic diameter in diastole normalized for body weight), whereas P-vel correlated more with left atrial (LA) enlargement indices (vertebral LA size, LA-to-aorta ratio, LA fractional shortening) and N-terminal pro-B-type natriuretic peptide. Peak velocity also showed closer association with International Small Animal Cardiac Health Council class than E-vel. Receiver operating characteristic analysis demonstrated E-vel effectively identified LV dilation, whereas P-vel was superior for detecting LA enlargement. Conclusions: E-vel may reflect LV dilation, whereas P-vel better may represent LA enlargement and functional burden, particularly in dogs with altered transmitral flow profiles. Clinical Relevance: Incorporating both E-vel and P-vel provides a more comprehensive assessment of cardiac remodeling in MMVD, supporting improved staging and monitoring in clinical practice.