Transcatheter Aortic Valve Replacement for Bioprosthetic Aortic Valve Failure

Bioprosthetic valves are increasingly used in patients with aortic stenosis. Compared with mechanical valves, bioprosthetic valves are associated with a lower risk of thromboembolic events and do not require long-term anticoagulation.1,2 However, bioprosthetic valves have limited durability; the best current valves can be expected to degenerate within 10 to 20 years, resulting in stenosis or regurgitation. Surgical valve replacement is the current standard of care for these patients. However, reoperative morbidity and mortality risk is significant, not only because of the complexity of reoperation but also because many of these patients have comorbidities, particularly advanced age.1–5Transcatheter heart valve (THV) implantation for native valve aortic stenosis has evolved as a viable, less invasive alternative to open heart surgery in selected patients.6 Recently, THV implantation within failed surgically implanted bioprostheses has proven feasible.7–10 Here, we review what is known of the potential and challenges of valve-in-valve (VinV) implantation in patients with failing surgical aortic bioprostheses.Bioprosthetic valves incorporate leaflets made from animal tissue. Xenografts are fashioned from porcine aortic valves, from more durable bovine pericardium, or rarely from porcine pericardium. Homografts are fashioned from human aortic valves. Tissue is generally preserved in glutaraldehyde, which cross-links collagen fibers, reducing antigenicity and in vivo enzymatic degradation.11 Various proprietary anticalcification treatments are commonly used. Surgical bioprostheses are commonly stratified into stented and stentless valves (Figure 1).Figure 1. Common bioprosthetic surgical valves. The Mosaic (Medtronic) valve could be implanted either intra-annularly or supra-annularly. Stented BioprosthesesStented valves are usually constructed with bovine pericardium or whole porcine aortic valves attached to a support structure such as a stent or frame. Current bioprosthetic frames are composed of alloy or polymer materials that absorb some of the forces acting on the leaflets. The frame of the bioprosthesis is responsible …