Abstract
BACKGROUND: Severe mitral regurgitation (MR) is closely associated with high hospitalization rates and progressive heart failure. Three-dimensional (3D) echocardiography (Echo) can quantify MR and structural abnormalities of the mitral annulus. Left atrial (LA) reservoir function, measured by speckle-tracking echocardiography (STE), has incremental prognostic value in patients with moderate and severe functional MR. However, previous studies have largely focused on the assessment of degenerative mitral regurgitation (DMR) using 3D transesophageal echocardiography (TEE). This study aimed to assess alterations in mitral valve structure and function in patients with severe MR using real-time 3D transthoracic echocardiography (TTE), to explore the risk factors of severe MR, and to analyze the correlation between severe MR and mitral valve geometric changes and LA remodeling. METHODS: In total, 50 consecutive patients with severe MR and 47 matched patients without MR were included in the study. Quantitative parameters of the mitral annulus and mitral leaflets were analyzed by Echo post-processing software, four-dimensional automated mitral valve quantification (4D Auto MVQ), and LA physiological function was analyzed by STE. Finally, a multivariate logistic regression analysis model was employed to identify the risk factors associated with severe MR. RESULTS: The quantitative 3D MV analysis revealed significant annular and leaflet remodeling in severe MR, including a significantly increased annulus area 3D (A3D; 8.49±2.28 vs. 4.75±0.98; P<0.001) and a higher non-planar angle (NPA; 161.82±14.20 vs. 154.60±11.67; P=0.008), accompanied by increased leaflet areas and lengths, and greater tenting indices (all P<0.001). LA phasic function was impaired in severe MR, with reduced left atrial reserve strain (LAS-R; 19.72±9.56 vs. 23.40±8.53; P=0.048) and reduced left atrial contractile strain (LAS-CT; -7.6±5.5 vs. -13.21±5.9; P<0.001), but no such significant difference was observed in relation to left atrial conduit strain (LAS-CD) (P=0.162). In the multivariate logistic regression analysis, an increased A3D emerged as the strongest predictor of severe MR [hazard ratio (HR): 14.575 (2.886-73.615), P=0.001]. In addition, impaired LA phasic function, including decreased LAS-R [HR: 1.465 (1.061-2.024), P=0.02] and decreased LAS-CT [HR: 2.183 (1.250-3.812), P=0.006], was independently associated with severe MR. CONCLUSIONS: Severe MR is closely related to morphological and functional changes in the mitral annulus, mitral leaflets, and LA. Mitral annular dilation may be the first and most significant factor contributing to severe MR.