Mitral Annular Dimensions and Geometry in Patients With Functional Mitral Regurgitation and Mitral Valve Prolapse: Implications for Transcatheter Mitral Valve Implantation.

OBJECTIVES: The aims of this study were to determine D-shaped mitral annulus (MA) dimensions in control subjects without significant cardiac disease and in patients with moderate to severe mitral regurgitation (MR) being considered for transcatheter mitral therapy and to determine predictors of annular size, using cardiac computed tomography.

BACKGROUND: The recently introduced D-shaped method of MA segmentation represents a biomechanically appropriate approach for annular sizing prior to transcatheter mitral valve implantation.

METHODS: Patients who had retrospectively gated cardiac computed tomography performed at our institution (2012 to 2014) and were free of significant cardiac disease were included as controls (n = 88; 56 ± 11 years of age; 47% female) and were compared with patients with moderate or severe MR due to functional mitral regurgitation (FMR) (n = 27) or mitral valve prolapse (MVP) (n = 32). MA dimensions (projected area, perimeter, intercommissural, and septal-to-lateral distance), maximal left atrial (LA) volumes, and phasic left ventricular volumes were measured.

RESULTS: MA dimensions were larger in patients with FMR or MVP compared with controls (area index 4.7 ± 0.6 cm(2)/m(2), 6.0 ± 1.3 cm(2)/m(2), and 7.3 ± 1.7 cm(2)/m(2); perimeter index 59 ± 5 mm/m(2), 67 ± 9 mm/m(2), and 75 ± 10 mm/m(2); intercommissural distance index 20.2 ± 1.9 mm/m(2), 21.2 ± 3.1 mm/m(2), and 24.7 ± 3.2 mm/m(2); septal-to-lateral distance index 14.8 ± 1.6, 18.1 ± 3.3, and 19.5 ± 3.4 mm/m(2) in controls and patients with FMR and MVP, respectively; p < 0.05 between controls and MR subgroups). Absolute MA area was 18% larger in patients with MVP than patients with FMR (13.0 ± 2.9 cm(2) vs. 11.0 ± 2.3 cm(2); p = 0.006). Although LA and left ventricular volumes were both independently associated with MA area index in controls and patients with MVP, only LA volume was associated with annular size in patients with FMR.

CONCLUSIONS: Moderate to severe MR was associated with increased MA dimensions, especially among patients with MVP compared with control subjects without cardiac disease. Moreover, unlike in controls and patients with MVP, annular enlargement in FMR was more closely associated with LA dilation.