Effect of Valve Design on the Stent Internal Diameter of a Bioprosthetic Valve: A Concept of True Internal Diameter and Its Implications for the Valve-in-Valve Procedure

The goal of this study was to provide a measurement of the true internal diameter (ID) of various surgical heart valves (SHV) to facilitate the valve-in-valve (VIV) procedure. During a VIV procedure, it is important to choose the right of the transcatheter heart valve (THV). Most users use the stent ID of an SHV to select the appropriate THV size. Echocardiography and computed tomography measurements are not yet standardized for measuring the ID of a variety of SHVs. Hence, we measured the true ID of SHV to assess the effect of valve design on the stent ID. Thirteen types of stented and 3 types of stentless valves were evaluated. True ID measurements were obtained using calipers and Hegar dilators. These were compared with the stent ID measurements. Fluoroscopy was used to confirm the impact of SHV designs on the true ID. Caliper measurements were found to be inaccurate and are hence not recommended. Hegar dilator measurements revealed a trend of reduction in stent ID. Porcine valves were most affected by their design, with reduction in the stent ID by at least 2 mm; pericardial valves with leaflets sutured inside the stent had the stent ID reduced by at least 1 mm, and SHV with leaflets sutured outside the stent had no effect on stent ID. In the majority of SHV designs, there is a reduction in the stent ID as a result of leaflet tissue. This is important in borderline sizes to avoid problems associated with oversizing and also to confirm suitability for the VIV procedure in the smaller label sizes of SHV.