Quantitative multi-slice computed tomography assessment of the mitral valvular complex for transcatheter mitral valve interventions part 2: geometrical measurements in patients with functional mitral regurgitation

Aims: Transcatheter mitral valve replacement (TMVR) is an emerging technology with the potential to treat patients with mitral regurgitation at excessive risk for mitral valve surgery. Geometrical measurements of the mitral valvular complex may have implications for the design of TMVR devices and for patient selection. This study sought to quantify the dynamic geometry of the mitral valvular complex in patients with significant functional mitral regurgitation (FMR) using multi-slice computed tomography (MSCT). Methods and results: MSCT images were acquired in 32 patients with symptomatic, significant FMR. Two independent observers analysed image sets using a dedicated software package and a standard measurement methodology. In patients with FMR, the mean mitral annulus intercommissural and aorto-mural diameters were, respectively, 41.5 +/- 5.2 mm and 38.7 +/- 5.9 mm in systole, and were 41.5 +/- 4.4 mm and 40.0 +/- 4.7 mm in diastole. In patients without MR, the diameters were, respectively, 33.6 +/- 5.1 mm and 28.8 +/- 8.0 mm in systole, and 36.2 +/- 4.5 mm and 31.6 +/- 7.9 mm in diastole. The obstacle-free zone below the mitral annulus averaged more than 20.0 mm and varied by less than 1 mm between systole and diastole, which is not statistically significant. The aorto-mitral angle was 129.7 +/- 10.5 degrees in systole and 131.0 +/- 9.4 degrees in diastole. Conclusions: The mitral annulus is larger in dimension, more circular, and less dynamic in patients with FMR. The obstacle-free zone below the mitral annulus is relatively constant during the cardiac cycle. Measurements of the mitral valvular apparatus vary considerably between patients, which suggests that tridimensional imaging will play an important role in the sizing of TMVR devices.