Design characteristics of a three-dimensional geometric aortic valve annuloplasty ring

Abstract

Objective: A full geometric annuloplasty ring could facilitate aortic valve repair. The purpose of this report was to document the design of such a ring using mathematical analyses of normal human aortic valve computed tomographic angiograms.

Methods: One-millimeter axial slices of high-resolution computed tomographic angiograms from 11 normal aortic roots were used to generate high-density x, y, and z coordinates of valve structures in Mathematica. Three-dimensional least squares regression analyses of leaflet-sinus coordinates were used to assess geometry of aortic valve and root structures.

Results: Normal valve geometry could be represented as three leaflet-sinus general ellipsoids nested within an elliptical aortic root. Minor-major diameter ratio of the valve base was 0.60 ± 0.07, and elliptical geometry extended vertically up the commissures. By contrast, leaflet-sinus horizontal circumferences were fairly circular (diameter ratios, 0.82-0.87), and the left coronary/noncoronary commissural post was located at the posterior base minor diameter-circumference junction, with the center of the right coronary leaflet opposite. Post location on the circumference was symmetrical, with a deviation of only ±2% to ±3% from 33.3% symmetry. Commissural posts flared outward by 5 to 10 degrees, and leaflet areas were statistically equivalent (P > 0.10). From end diastole to midsystole, the aortic root became less elliptical (diameter ratio increased by 0.15), but root area expanded minimally (less than +5%). A one-piece rigid annuloplasty ring was designed with 2:3 base ellipticality, three 10-degree outwardly flaring symmetrical posts, and post height = base circumference/2π.

Conclusions: A three-dimensional aortic annuloplasty ring was designed that could prove useful for enhancing applicability and stability of aortic valve repair.