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INTRODUCTION

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Transcatheter aortic valve replacement (TAVR) has been shown to improve mortality and quality of life in patients with severe aortic stenosis who are designated inoperable or high risk for surgical aortic valve replacement (SAVR).1-5 The first implantation of a transcatheter heart valve (THV) in the aortic position was performed by Cribier et al6 to treat an inoperable patient with severe symptomatic aortic stenosis. From the development of the porcine model to the first clinical implantation in the aortic position, the makeup of a THV was a foldable biological cardiac valve sewn inside an expandable stent frame. This device would be crimped onto a balloon in order to deploy the THV via inflation. With this concept, the technology has emerged as one of the most transformative in the field of interventional cardiology. Given the initial focus on development of a balloon-expandable THV to facilitate TAVR, the largest experiences with TAVR are with balloon-expandable THVs. The main objectives of this chapter are to review the available devices, methods of implantation, clinical outcomes, valve hemodynamics, and durability associated with these systems.

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THE BALLOON-EXPANDABLE TRANSCATHETER HEART VALVE

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The initial large-scale clinical experience with the balloon-expandable THV was with the Cribier-Edwards balloon-expandable aortic stent valve (Edwards Lifesciences, Irvine, CA). This consisted of a trileaflet tissue valve composed of equine pericardium mounted on a stainless steel frame.6

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Subsequent improvements to this system led to the development of the second-generation Edwards SAPIEN THV (Edwards Lifesciences). Major differences between the first- and second-generation devices were the incorporation of pretreated bovine pericardium as the material for the valve leaflets, which had been demonstrated to decrease valve calcification, in addition to a polyethylene terephthalate skirt, which extended to a larger expanse of the stent frame, thus improving sealing and potentially reducing paravalvular regurgitation (PVR).7 The 2 sizes of this device, the 23- and 26-mm diameter THVs, could be inserted via 22- and 24-Fr delivery systems for transfemoral (TF) TAVR and through a 29-Fr sheath via transapical access for patients without vascular adequate for the TF approach.

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The third-generation of the balloon-expandable Edwards THVs is the SAPIEN XT THV (Edwards Lifesciences). This also consists of a trileaflet pericardial bovine valve, but the leaflets have a scallop shape to improved leaflet durability and the valve is mounted on a cobalt chromium stent frame.7 The latter decreases the profile of the THV, given the thinner struts and fewer rows between commissures. The SAPIEN XT THV is available in 23-, 26-, and 29-mm sizes in the United States, with a 20-mm size available internationally. The sheath sizes are smaller than those of the previous generation Edwards THVs because of the lower profile characteristics, as described earlier. The NovaFlex+ delivery system replaced the original RetroFlex3 sheath used for the previous generation device (Edwards Lifesciences). Through this system, the 20- and 23-, 26-, and 29-mm SAPIEN XT can be advanced ...

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