Validation of a Holographic Display for Quantification of Mitral Annular Dynamics by Three-Dimensional Echocardiography

Abstract

Three-dimensional (3D) echocardiography with multiplanar reconstruction (MPR) is used clinically to quantify the mitral annulus. MPR images are, however, presented on a two-dimensional screen, calling into question their accuracy. An alternative to MPR is an autostereoscopic holographic display that enables in-depth visualization of 3D echocardiographic data without the need for special glasses. The aim of this study was to validate an autostereoscopic display using sonomicrometry as a gold standard. In 11 anesthetized open-chest pigs, sonomicrometric crystals were placed along the mitral annulus and near the left ventricular apex. High-fidelity catheters measured left atrial and ventricular pressures. Adjustments of pre- and afterload were done by constriction of the inferior vena cava and the ascending aorta, respectively. Three-dimensional epicardial echocardiography was obtained from an apical view and converted to the autostereoscopic display. A 3D virtual semitransparent annular surface (VSAS) was generated to measure commissure width (CW), septal-lateral length, area of the mitral annular surface, nonplanarity angle, and the annular height-to-commissure width ratio in mid-systole and late diastole. Mitral annular measurements from the 3D VSAS derived from the 3D echocardiographic images and autostereoscopic display correlated well with sonomicrometry over a range of loading conditions: CW length (r=0.98, P<.00001), septal-lateral length (r=0.98, P<.00001), annular surface area (r=0.93, P<.001), nonplanarity angle (r=0.87, P<.001), and annular height-to-commissure width ratio (r=0.85, P<.01). The 3D VSAS showed better agreement with the sonomicrometric measurements compared with MPR. Mitral annular measurements using 3D VSAS correlate well with sonomicrometry over a range ofloading conditions and may represent a powerful tool for noninvasive quantification of mitral annular dynamics.