ANATOMICAL AND HEMODYNAMIC PHENOTYPES OF THE MITRAL VALVE IN PATIENTS WITH MITRAL REGURGITATION

Abstract

Background: Mitral regurgitation (MR) is a heterogeneous valvular disorder in which structural abnormalities of the mitral valve apparatus produce distinct alterations in transvalvular flow and cardiac loading. Anatomical phenotypes, including rheumatic leaflet restriction, myxomatous mitral valve prolapse, and flail leaflet, may therefore have different echocardiographic and hemodynamic characteristics. Characterizing these phenotypes may improve understanding of the mechanisms underlying MR and its associated cardiac remodeling. Objective: To characterize the anatomical phenotypes of the mitral valve among patients with mitral regurgitation and to assess their associated echocardiographic and hemodynamic characteristics. Methods: A hospital-based observational cross-sectional study was conducted at Mardan Medical Complex, Mardan, Pakistan, from June to December 2021. A total of 120 adult patients with echocardiographically confirmed mitral regurgitation were included. Two-dimensional transthoracic echocardiography was used to assess mitral leaflet morphology and mobility, scallop involvement, commissures, chordae tendineae, papillary muscles, mitral annular dimensions, left atrial and left ventricular dimensions, and left ventricular ejection fraction. Doppler echocardiography was used to assess peak transmitral velocity, mean transmitral gradient, effective regurgitant orifice area (EROA), and regurgitant volume. Patients were categorized according to their predominant anatomical phenotype. Continuous and categorical variables were summarized using appropriate descriptive statistics, with comparisons performed using parametric or non-parametric tests as appropriate. Results: Of the 120 patients, 78 (65.0%) were male and 42 (35.0%) were female. Rheumatic leaflet restriction was the predominant anatomical phenotype, identified in 78 patients (65.0%), followed by myxomatous mitral valve prolapse in 22 (18.3%) and flail leaflet in 12 (10.0%). The remaining patients had less frequent phenotypes, including functional/secondary MR, mixed rheumatic disease, annular dilatation, and ischemic tethering. Significant differences between the major anatomical phenotypes were observed for mitral annular dimension (p=0.009), mitral valve area (p<0.001), peak transmitral velocity (p<0.001), mean transmitral gradient (p<0.001), EROA (p<0.001), regurgitant volume (p<0.001), left atrial dimension (p=0.023), and LV end-diastolic dimension (p=0.003). EROA was positively correlated with left atrial dimension (ρ=0.290, p=0.001) and LV end-diastolic dimension (ρ=0.253, p=0.005), while regurgitant volume was positively correlated with LV end-diastolic dimension (ρ=0.259, p=0.004). Conclusion: Distinct mitral valve anatomical phenotypes demonstrate different echocardiographic and hemodynamic profiles in patients with mitral regurgitation. The predominance of rheumatic leaflet restriction in this cohort highlights the continuing importance of rheumatic mitral valve disease in the regional population. The associations between regurgitant parameters and cardiac chamber dimensions further support the physiological link between abnormal valve structure, altered transvalvular flow, and cardiac remodeling. An integrated echocardiographic assessment combining mitral valve morphology, Doppler hemodynamics, regurgitation severity, and chamber remodeling may provide a more comprehensive characterization of mitral regurgitation.