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

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.