title: Transcatheter valve-in-valve implantation: a systematic review of literature.
abstract: BACKGROUND
  Transcatheter aortic valve implantation (TAVI) has become an alternative to open surgery in those deemed high risk. The purpose of this study was to evaluate the effectiveness and outcomes of this emerging procedure. We have examined available literature to provide an overview of valve-in-valve implantation using transcatheter heart valves (THVs) in aortic, mitral, pulmonary, tricuspid positions.
  
  
  METHODS
  A systematic search was conducted using MEDLINE, PubMed, EMBASE, Current Contents Connect, Cochrane library, Google Scholar, Science Direct, and Web of Science.
  
  
  RESULTS
  Only 61 studies met full criteria and were included the review. This included 31 studies reporting transcatheter aortic valve-in-valve implantation, mitral valve-in-valve implantation (13 studies), tricuspid valve-in-valve implantation (12 studies), and pure native aortic valve regurgitation (nine studies). One of the limitations of this review is that most of the studies included were case reports, together with some case series.
  
  
  CONCLUSIONS
  Valve-in-valve implantation can be considered as an acceptable alternative to conventional open heart surgery for elderly high-risk surgical patients with bioprosthetic degeneration. Long-term follow-up of treated patients will be necessary to establish the true role of valve-in-valve implantation for bioprosthetic degeneration. Patients should be evaluated on an individual basis until outcomes are proven in large cohort studies or randomised trials.
authors.affiliation: Department of Cardiology, Blacktown Hospital, and University of Western Sydney, Sydney, NSW, Australia. Electronic address: jwalant_21@yahoo.com.
authors.forename: Jwalant
authors.initials: J
authors.lastname: Raval
authors.affiliation: The Whiteley-Martin Research Centre, Discipline of Surgery, The University of Sydney, Nepean Hospital, Sydney, NSW, Australia.
authors.forename: Vinayak
authors.initials: V
authors.lastname: Nagaraja
authors.affiliation: The Whiteley-Martin Research Centre, Discipline of Surgery, The University of Sydney, Nepean Hospital, Sydney, NSW, Australia.
authors.forename: Guy D
authors.initials: GD
authors.lastname: Eslick
authors.affiliation: Department of Cardiology, Blacktown Hospital, and University of Western Sydney, Sydney, NSW, Australia.
authors.forename: A Robert
authors.initials: AR
authors.lastname: Denniss
mesh_terms: D001022:Aortic Valve Insufficiency / Q000601:surgery*; D006801:Humans; D016239:MEDLINE; D065467:Transcatheter Aortic Valve Replacement / Q000295:instrumentation* / Q000379:methods*
keywords: Off-label indications; Pure aortic regurgitation; TAVI; Transcatheter aortic valve implantation; Transcatheter heart valves; Valve-in-valve