Valve-in-valve transcatheter aortic valve implantation: The issues behind crossing a bioprosthesis.

Valve-in-valve transcatheter aortic valve implantation (ViV TAVI) is rapidly arising as a safe and effective alternative to redo-surgery in the treatment of bioprostheses deterioration. While scientific community is currently focusing its attention on the most common limitations related to this procedure, such as the risk of coronary obstruction and patient-prosthesis mismatch, data regarding the first step of a ViV TAVI, the crossing of a degenerated bioprosthesis, are still lacking. The aim of this review is to analyze the available information about bioprosthesis crossing, to show the inherent challenges encountered by interventional cardiologists during valve crossing and to describe the current strategies to perform a correct crossing.