Quantification of Stent Creep by Three-Dimensional Transesophageal Echocardiography in Patients Undergoing Transcatheter Aortic Valve-in-Valve Implantation for Failed Bioprostheses

Abstract

Background: Transcatheter aortic valve-in-valve implantation (aVIV) has been used to treat bioprosthetic failure due to "stent creep", defined as inward flexion or bending of stent posts. The aim of this study was to develop quantitative three-dimensional transesophageal echocardiography (3D-TEE) geometric analysis of failed bioprostheses to determine the incidence of stent creep in patients undergoing aVIV and its contribution to the hemodynamics of those valves.

Methods: We retrospectively examined the 3D-TEE of 22 consecutive patients (age 74.4 ± 11.3 years; M/F = 12/10) who underwent aVIV for failed bioprostheses. The modes of bioprosthesis failure included stenosis (n = 8), regurgitation (n = 9), and combined (n = 5). The degree of stent creep was assessed by calculating the triangular area obtained by projecting the apex of stent posts on a reconstructed plane. This measured area was divided by that of the regular triangle defined by the base of stent posts to calculate a ratio, which we termed the "stent creep ratio" (SCR).

Results: The mean SCR was lower in the patients with failed prostheses than that in the controls (0.82 ± 0.16 vs. 0.96 ± 0.05, p = 0.02). The SCR was negatively correlated with the peak trans-aortic pressure gradient (r = -0.62, p < 0.01). An SCR cut-off point of 0.79 was associated with aortic peak velocity > 4 m/s (AUC = 0.81, sensitivity = 0.79, specificity = 0.83). Fourteen of the 22 patients had pre- and post-aVIV 3D-TEE, and the SCR was corrected satisfactorily from 0.81 ± 0.13 to 1.04 ± 0.19 (p < 0.01).

Conclusions: SCR measured by 3D-TEE is feasible to quantitatively evaluate stent creep. Stent creep is an important mode of structural deterioration in surgical bioprostheses, which can be treated by aVIV.

Keywords: Aortic valve-in-valve; Bioprosthetic valve dysfunction; Stent creep ratio.

Figure 1

Calculation of stent creep ratio (SCR). (A) Ideally, three stent posts are perpendicular to the annular ring. As a results, the area of tip-triangle (blue) should equal the bottom-triangle (orange). Once stent creeping (SC) develops, tip-triangle shrinks and the ratio of tip- to bottom-triangle will be less than 1.0. (B) By three-dimensional transesophageal echocardiography and multi-planar reconstruction technique, the three tips of stent posts could be identified. (c) A case of SC. The tip-triangle area is calculated as 0.82 cm² by Heron’s formula. (D) Bottom triangle is calculated basing the inner diameter of 21 mm Edwards standard (CE-S) bioprosthesis. The SCR is 0.82/1.18 = 0.69.

Figure 2

Predicting peak aortic pressure gradient > 4 m/s with SCR by receiver operating characteristic curve analysis.

Figure 3

SCR of 14 failed bioprostheses before and after aVIV.