Three-Dimensional Mitral Valve Morphology and Age-Related Trends in Children and Young Adults with Structurally Normal Hearts Using Transthoracic Echocardiography

Background: The mitral valve has a complex three-dimensional (3D) morphology that is incompletely described by two-dimensional echocardiography (echo). Three-dimensional echo provides a more robust tool to analyze the mitral valve. The shape of the mitral annulus and leaflets, and differences with age, have not been described by 3D echo in normal children. Our objective was to characterize and quantify the 3D mitral valve morphology in children with normal transthoracic echocardiograms over a broad spectrum of age and to identify differences in valve shape with age. Methods: Three-dimensional midsystolic mitral valve models were constructed in 100 children and young adults with normal echocardiograms using 3D transthoracic images. Annular and leaflet metrics were quantified and regression equations were prepared. Interuser and intrauser variability was measured. Results: Two hundred fifty patients, from neonate to young adult, were retrospectively reviewed to obtain 100 evaluable patients (40% evaluable). The annular height to commissural width ratio of the mitral valve (saddle shape'') was preserved across age (median 24.3, IQR 21.8-28.1). Three-dimensional mitral valve area, length, and volume parameters were linearly related to body surface area (P <.001). The ratio of anterior to posterior leaflet length and posterior leaflet angle increased with body surface area (P =.0004 and.002, respectively) suggesting posterior movement of the coaptation line. Two-dimensional lateral annular diameter underestimated 3D lateral annular metrics (P <.001, mean difference 20-22%) but was highly correlated (R > 0.87, P <.001). Interuser and intrauser variability were acceptable. Conclusions: Assessment of 3D mitral valve morphology in children is possible in a modern clinical pediatric echocardiography laboratory using transthoracic images, although further optimization of imaging is needed. The saddle shape of the mitral annulus was preserved across age and size. Most mitral valve parameters increased linearly with patient size. Further investigation is warranted to explore changes in valve morphology in the pediatric population in health and with disease.