Mitral Valve-In-Valve: Defining the Indication Limits by in vitro Hydrodynamic Tests in a Brazilian Transcatheter Prosthesis

Introduction: Reoperations in cardiac surgery represent a clinical challenge, particularly because of the higher rate of perioperative morbidity and mortality. Mitral valve reoperation owing to bioprosthesis dysfunction, transcatheter treatment with a prosthesis implantation over the prosthesis has emerged as an alternative, especially for patients with a previous approach. In this study, we analyzed the hydrodynamic behavior of transcatheter prosthesis implantation in conventional mitral bioprostheses through hydrodynamic tests and produced a recommendation for the size of transcatheter valve most adequate for valve-in-valve procedure. Methods: Mitral bioprostheses were attached to a flow duplicator and different combinations of transcatheter prostheses were implanted inside. The equipment simulates the hydrodynamic behavior of the valves submitted in vitro and determines transvalvular pressures and flow parameters. Results: All tests could be performed. Better hydrodynamic performance occurred for transcatheter prostheses 1 mm smaller than bioprostheses, except for the 27-mm bioprostheses. Effective valve areas (cm2) and transvalvular gradients (mmHg) were, respectively: Bioprosthesis x Inovare: 27 x 28 mm: 1.65 and 5.95/29 x 28 mm and 31 x 30 mm: 2.15 and 3.6. Conclusion: The mitral valve-in-valve implantation proved to be feasible in vitro. The use of 27-mm bioprostheses should be judicious, with preference for a 26-mm transcatheter valve. In the 29 and 31-mm bioprostheses, the implantation was very satisfactory, with good effective valve areas and transvalvular gradients, with preference for smaller transcatheter valves.