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Transcatheter aortic valve implantation (TAVI) represents a novel technology for treating patients with severe symptomatic calcific aortic stenosis at high or prohibitive surgical risk. In patients at excessive surgical risk, TAVI substantially reduces mortality compared to medical treatment,1 and in high risk cohorts provides similar safety and efficacy to surgical aortic valve (SAV) replacement.2
More recently, the remit of transcatheter heart valve (THV) technology has been expanded beyond that initially conceived: patients at lower surgical risk are being treated despite a lack of evidence in this patient populationw1; and novel implantation techniques, such as the transaortic approach, have been developed.w2 Perhaps the most notable adaptation of this technology is the treatment of patients with failing surgical bioprosthetic valves. In 2007, Wenaweser and colleagues reported the implantation of a Medtronic CoreValve (Medtronic CV, Luxembourg S.a.r.l.) into a degenerated surgical aortic bioprosthesis.3 Since this first case, numerous transcatheter aortic valve in surgical aortic valve (TAV-in-SAV) procedures have been performed,4–7 w3–11 and experienced physicians are adapting current THVs for treatment of failing surgical atrioventricular8 w12 and pulmonary bioprostheses.9
Design characteristics of surgical bioprostheses
Successful valve-in-valve (VIV) procedures are dependent on a thorough understanding of the design characteristics and failure modes of surgical bioprosthetic valves. Surgical bioprostheses are constructed as either stented or stentless valves (figure 1), while the valve leaflets are of xenograft (porcine aortic valve or bovine pericardium) or homograft origin.10
Stented valves usually consist of a base ring covered by a fabric sewing cuff from which a stent or frame arises to support the valve leaflets (figure 2). The base ring may be circular or scalloped and is constructed from a variety of metal …
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