Transcatheter aortic valve replacement for bioprosthetic aortic valve failure: the valve-in-valve procedure.

2542 B ioprosthetic valves are increasingly used in patients with aortic stenosis. Compared with mechanical valves, bio-prosthetic valves are associated with a lower risk of thrombo-embolic 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. Transcatheter 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 bio-prostheses 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). Stented valves are usually constructed with bovine peri-cardium 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 bio-prosthesis is responsible for its unique fluoroscopic appearance (Figure 2). The frame is attached to a basal ring, which may be circular or scallop shaped. Typically, the basal ring is covered with a fabric sewing cuff that facilitates suturing to native tissue. Bioprosthetic valves can be represented by several dimensions (Figure 3). The manufacturer's label size generally corresponds to the external diameter of the inflow portion, which matches the annular measurements made by the implanting surgeon using sizing tools. However, the inner diameter of the valve is the most relevant measure for VinV procedures. Other relevant measures include post height, leaflet height, and position of the valves within the aortic root. Initially, most bioprosthetic aortic valves were implanted in the plane of the …