Two Faces of Mitral Stenosis: Uncovering Structural and Hemodynamic Signatures of Rheumatic and Mitral Annular Calcification–Induced Disease

Background Mitral annular calcification (MAC) is common and associated with increased cardiovascular risk and, when severe, mitral stenosis (MS). MAC‐related MS differs anatomically and hemodynamically from rheumatic MS (RMS), challenging standard diagnostic methods. This study compares structural and flow characteristics, including kinetic energy losses, across MAC‐related MS, RMS, and normal mitral valves, and evaluates the applicability of conventional diagnostic metrics in MAC. Methods Three‐dimensional transesophageal echocardiographic data sets from 70 patients (22 normal mitral valves, 26 RMS valves, 22 MAC valves) were used to obtain linear, area, and volumetric measurements for valve comparison. Representative valves from each group were converted into 3‐dimensional silicone models for in vitro testing in a heart flow simulator. Transmitral flow was assessed with particle image velocimetry, flow energetics were quantified, and coefficients of contraction were derived from geometric and effective orifice areas. Results Compared with RMS, MAC‐related MS had smaller anteroposterior dimensions, reduced valve volume, and lower coefficients of contraction. MAC demonstrated the highest transmitral velocities and energy dissipation in vitro. Unlike the normal model, neither MAC nor RMS produced a consistent transmitral vortex ring. Despite having a larger geometric orifice, MAC MS produced a greater pressure drop than RMS, likely due to increased flow disruption and lower coefficients of contraction. Conclusions MAC‐related MS represents a unique pathophysiological entity, characterized by distinct structural and hemodynamic features. These findings underscore the necessity for disease‐specific diagnostic frameworks and multimodality imaging strategies to inform clinical decision making and guide emerging therapeutic approaches.