Integration of mitral regurgitant fraction with routine echocardiographic variables in assessment of myxomatous mitral valve disease.

Abstract

INTRODUCTION/OBJECTIVES: In humans with mitral valve disease, integration of echocardiographic variables with quantified mitral regurgitation (MR) is recommended. Quantification of MR has not been widely adopted in dogs. Mitral regurgitant fraction (MR%) has not been systematically reported in relation to other echocardiographic variables in myxomatous mitral valve disease (MMVD). ANIMALS, MATERIALS AND METHODS: Echocardiograms from 237 small-breed dogs with MMVD that included calculation of MR% were identified retrospectively. Mitral regurgitant fraction, monodimensional and bidimensional variables, estimates of filling pressure, forward flow, left ventricular early inflow outflow index (LVEIO), tricuspid regurgitant velocity, and systolic blood pressure are reported in preclinical MMVD and at the onset of American College of Veterinary Internal Medicine stage C congestive heart failure (C-CHF). The relationship of MR% to other variables is described, and correlations are determined. The discriminatory ability of variables in diagnosing stage C-CHF was evaluated with receiver operating characteristic analysis. RESULTS: All echocardiographic variables correlated to MR% by univariable analysis (all P values<0.0001). The LVEIO (&#x3c1; = 0.81), left atrial volume indexed to body weight (&#x3c1; = 0.76), and left ventricular end-diastolic volume indexed to body weight (&#x3c1; = 0.76) showed the strongest correlations. Patients with stage C- CHF had a median MR% of 83% (interquartile range: 79-85%). Mitral regurgitant fraction (area under the curve [AUC]: 0.97, 95% confidence interval [CI]: 0.95-0.99, P<0.0001), LVEIO (AUC: 0.96, 95% CI: 0.93-0.99, P<0.0001), and left atrial volume indexed to body weight (AUC: 0.96, 95% CI: 0.93-0.98, P<0.0001) had the highest areas under the receiver operating characteristic curve. STUDY LIMITATIONS: This is a single-operator retrospective study. CONCLUSIONS: Mitral regurgitant fraction is strongly correlated with echocardiographic variables used in assessment of MMVD. Integration of MR% may help stage disease, clarify equivocal signs, and guide management.