Aortic Valve-in-Valve Implantation: Impact of Transcatheter-Bioprosthesis Size Mismatch

Background and aim of the study: Transcatheter aortic valves (TAVs) provide minimally invasive treatment for high-risk patients with severe native aortic stenosis. While the off-label application of TAV for degenerative bioprosthetic stenosis (valve-in-valve therapy) is attractive, few cases have been reported. If the rigid annulus and stent posts of bioprostheses prevent full expansion of the TAV, the hemodynamic performance may be compromised. The study aim was to evaluate the use of a 23 mm TAV within normal bioprostheses of equivalent or smaller orifice sizes. Methods: Twelve TAVs designed to mimic the 23 mm Edwards SAPIEN valve were created using stainless steel stents and trileaflet pericardial valves. A custom-built pulse duplicator was used to measure the hemodynamic performance of the TAV within 19, 21 and 23 mm Edwards pericardial bioprostheses. The transvalvular gradient, effective orifice area (EOA) and regurgitant volume were used to evaluate valve-in-valve therapy for each valve size. Results: The TAV demonstrated similar hemodynamics to the Edwards SAPIEN valve (mean pressure gradient 6.68 +/- 2.11 mmHg and EOA 2.07 +/- 0.35 cm(2)). Acceptable valve-in-valve hemodynamics were achieved only in the 23 mm bioprosthesis after TAV implantation, with no significant change in mean pressure gradient (5.93 +/- 0.87 to 8.27 +/- 1.19 mmHg, p = 0.052) and EOA (2.13 +/- 0.15 to 1.79 +/- 0.15 cm(2), p = 0.053). In 19 and 21 mm valves, the excess pericardial tissue relative to the stent EOA resulted in severe and moderate stenosis, respectively. The mean pressure gradient increased from 16.18 +/- 2.20 mmHg to 45.53 +/- 12.54 mmHg (p = 0.004) in 19 mm bioprostheses, and from 11.84 +/- 1.88 mmHg to 28.18 +/- 9.03 mmHg (p = 0.004) in 21 mm bioprostheses. Furthermore, the EOA was reduced from 1.28 +/- 0.1 to 0.78 +/- 0.11 cm(2) (p <0.001) in 19 mm valves, and from 1.51 +/- 0.15 to 1.01 +/- 0.19 cm(2) (p <0.001) in 21 mm bioprostheses. The TAV resulted in an increased regurgitant volume for all valve sizes. Conclusion: Oversized TAVs are constrained by rigid bioprostheses, creating hemodynamic complications. Patients with 19 and 21 mm Edwards pericardial bioprostheses may be poor candidates for valve-in-valve therapy with the currently available technology.