The value of a novel three-dimensional mitral valve index in the assessment of the haemodynamic severity of rheumatic mitral stenosis

Background: Rheumatic mitral stenosis (MS) is characterised by structural alterations that reduce the size of the valvular orifice. In addition, changes in valve geometry may have haemodynamic consequences that extend beyond the narrowed orifice, influencing the overall clinical presentation of MS. The aim of this study was to develop an index to assess the haemodynamic severity of the stenosis. Methods: A total of 186 patients with rheumatic MS who underwent comprehensive three-dimensional (3D) transoesophageal echocardiographic assessment were included. Dedicated software was used to extract a range of morphological variables to evaluate mitral valve geometry, including diameter, area, height, volume, and the aortic–mitral angle. To quantify the volume enclosed within the stenotic structure, we developed the 3D Doming Index (DI), calculated by dividing the valvular volume (tenting volume) by the theoretical volume of a cylinder generated by the mitral annulus and valvular height (tenting height). Linear regression models were employed to identify determinants of the mean pressure gradient. Results: The 3D Doming Index demonstrated a significant association with the transmitral pressure gradient in the multivariate model, after adjusting for confounders including age, sex, heart rate, pulmonary artery systolic pressure, net atrioventricular compliance (C_n), and left atrial volume. Incorporation of the 3D Doming Index into the model improved overall performance. Conclusions: The geometric configuration of the mitral valve contributes to the haemodynamic burden of obstruction in rheumatic MS. The 3D Doming Index offers valuable insight into the relationship between valve anatomy and the resultant haemodynamic impact of the stenosis.