158 Circularity Index of deployed Edwards Sapien aortic valve bioprosthesis

Abstract

Transcatheter aortic valve replacement is a new alternative to heart surgery in selected patients. The balloon expandable Edwards-Sapien bovine valve is mounted in a stainless-steel stent with a maximal opening diameter of 23 or 26mm. Recent observational, anatomical study suggests that a distorted stent could produce valvular dysfunction impairing the long-term results. The Edwards Sapien bioprosthesis showed to have an optimal deployment and a high radial force in vitro. To further assess its deployment in patients with severe calcified aortic stenosis, we conducted a prospective study to analyze the circularity of the cross-sectional area of the deployed stent. Optimal cross sectional projection of the expanded stent was selected on X-ray after the procedure. Images were analyzed and the corresponding profile of the stent was described by means of a polygon, for each valve, using two computer programs: 1) to measure the coordinates of the points composing this polygon and 2) to compute the corresponding cross-sectional areas. We defined a circularity index to measure the departure of this curve from the (best) theoretical conditions of a circle, the ratio of its area to the squared perimeter as a percent value of the corresponding ratio for a circle (1/4xpi=0.079). 23 patients were implanted (23 mm in 9 and 26 mm in 14). Final perimeters from cross-sectional areas of deployed stents were similar to the nominal perimeter in both sizes prosthesis (94–98% from the reference values). Mean circularity index was 0.078 + 0.001, with a mean perceptual difference of 1.6 (98.4% of similarity with a perfect circle). Most of the Edwards Sapien valve cross-sectional areas are circular after deployment even within heavily calcified native valves, confirming the high radial force of the stent. The circularity index can be considered a useful parameter to assess the quality of opening of transcatheter aortic valves.