Transcatheter valve-in-valve implantation for degenerated bioprosthetic aortic and mitral valves.

INTRODUCTION: Redo surgery still is the treatment of choice for degenerated bioprosthesis. However, as far as elderly patients with concomitant comorbidities are concerned, the standard reoperation carries additional operative risks and, therefore, minimally invasive procedures must be prioritized. AREAS COVERED: During the last ten years, transcatheter procedures in native valves have become a standard technique in several centers with excellent procedural and mid-term results. Similarly, implantation of transcatheter stent-valves within degenerated aortic and mitral bioprosthesis, the 'valve-in-valve' procedure (V-in-V), represents a valid alternative to redo surgery in patients with high-risk surgical profiles. New challenges for V-in-V are the transcatheter stent-valve deployment in hostile targets (stented bioprosthesis with externally mounted leaflets, stentless valves, small bioprostheses), and avoid complications as delayed atrial embolization of mitral implantation and V-in-V thrombosis. Moreover a continuous ameliorated design of the devices on the market and new transcatheter stent-valves are recently developed in order to improve the outcome and safety of V-in-V treatment. Expert commentary: We reviewed the clinical outcomes and the procedural details of published transcatheter aortic and mitral valve-in-valve series focusing, in particular, on data from the Valve-in-Valve International Data registry (VIVID), and we provide a practical guide for valve sizing and stent-valve positioning.