Ann Thorac Surg 2006;82:713-714
© 2006 The Society of Thoracic Surgeons
New technology
Invited commentary
Thomas A. Vassiliades, Jr, MD
Division of Cardiothoracic Surgery, Emory University School of Medicine, 1365A Clifton Road, NE, Atlanta, GA 30322
(Email: thomas.vassiliades{at}emoryhealthcare.org).
The article by Attmann and coworkers [1] presents the results of a chronic animal feasibility study of using a self-expanding nitinol stent supporting a bovine jugular vein valve for percutaneous pulmonary valve replacement, and represents continuing work previously reported by the same group [2]. In this experiment, 9 sheep received the nitinol stented bovine valve percutaneously with 2 animals experiencing lethal bleeding complications attributed to the procedure and 1 animal succumbing to endocarditis at 2.5 months. The remaining 6 animals, surviving to 3 months, demonstrated good valve function with one mild central insufficiency and no paravalvular leaks. This is early pioneering work, and while the vascular complications of insertion are concerning, the investigators and readers should not lose sight of the true significance of this work (ie, the limitations of balloon-expandable stent technology to treat calcified or severely angulated right ventricular outflow tracts). Self-expanding stents may be an answer to this problem, although nitinol-based stents, as used in this animal study, may not possess enough radial force (0.1 Newton) to overcome even the most minimal stricture or calcification. As an example, most of the current work in percutaneous aortic valve replacement has been with stainless steel stents. Regardless, self-expanding stents possess some properties that may make them superior to their balloon-expanding stent counterparts. By virtue of their continuously exerted outward radial force, self-expanding stents are more likely to adapt to ongoing tissue property changes at the implantation site and therefore less prone to migration. Furthermore they possess greater flexibility than the stiffer balloon-expanded stents that would provide an advantage when one expects the stent to conform to a more complicated anatomic geometry.
Although there may be less anatomic hurdles with percutaneous pulmonary valve replacement than with percutaneous aortic valve replacement, many important issues remain such as the size of the introducer devices and the durability of bioprosthetic valve prostheses subjected to crimping for implantation. Notwithstanding, Attman and colleagues [1] have greatly enriched the rapidly growing body of knowledge in this field and should be encouraged to continue their investigations.
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References
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- Attmann T, Quaden R, Jahnke T, et al. Percutaneous pulmonary valve replacement3-month evaluation of self-expanding valved stents. Ann Thorac Surg 2006;82:708-714.[Abstract/Free Full Text]
- Attmann T, Jahnke T, Quaden R, et al. Advances in experimental percutaneous pulmonary valve replacement Ann Thorac Surg 2005;80:969-975.[Abstract/Free Full Text]
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