Invited commentary

Abstract

Although enhanced knowledge and technological advances are making the total correction for the majority of congenital heart defects routine and safe, either the initial implantation of a biological valved conduit or conduit replacement inevitably lead to repeat surgery and represent one of the more frustrating issues of our field in need of a long-term solution. For reconstruction of the right ventricular outflow tract, valved homograft conduits have the best track record and are considered the gold standard. However, for small patients, small sized homografts are scarce and even when larger ones can be downsized (ie, bicuspidized), they present limitations with regards to patient-conduit size mismatch and resistance to degeneration, and they fare as poorly as other known xenograft valves. The current article [1Schreiber C. Sassen S. Kostolny M. et al.Early graft failure of small-sized porcine-valved conduits in reconstruction of the right ventricular outflow tract.Ann Thorac Surg. 2006; 82: 179-186Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar] is the third clinical report on the Shelhigh No-React porcine-valved conduit, confirming the poor results already observed by others [2Ishizaka T. Ohye R.G. Goldberg C.S. et al.Premature failure of small-sized Shelhigh No-React porcine pulmonic valve conduit model NR-4000.Eur J Cardiothoracic Surg. 2003; 23: 715-718Crossref PubMed Scopus (34) Google Scholar, 3Pearl J.M. Cooper D.S. Bove K.E. Manning P.B. Early failure of the Shelhigh pulmonary valve conduit in infants.Ann Thorac Surg. 2002; 74: 542-548Abstract Full Text Full Text PDF PubMed Scopus (30) Google Scholar], which lead the authors to abandon implantation in their own practice, and to discourage the use of this conduit by others. The fact that 62% of their patients were under 1 year of age illustrates the problem known to us all in finding appropriately sized small homografts, and this justifies their trial to find a better and more practical “off the shelf” alternative. However, just as with other xenografts, the authors found that the Shelhigh No-React formed an extensive neointimal peel leading to early conduit stenosis and failure, although gross calcification was not noted. Despite efforts by the manufacturers to produce a nonimmunogenic product, the presence of a nonspecific macrophage and granulocyte-mediated inflammatory response still pointed to a foreign-body reaction. Therefore, the concerns and condemnation of this conduit by the authors are validly argued and well illustrate the ongoing search for an ideal alternative to reconstruct the right ventricular outflow tract. Accordingly the inevitable life-long threat of multiple reoperations for any given patient and the associated risks continue to motivate many research groups to focus their efforts on the quest for the tissue-engineered grail (ie, the “perfect biological valve”). Curiously the authors gave no justification for full heparinization followed by oral anticoagulation to an international normalized ratio of 2 to 3 for at least 3 months, and they did not state if some patients eventually required longer anticoagulation and for which reasons. Most centers would agree that unless a proven advantage in terms of patient benefit or conduit longevity or both can be demonstrated with this practice, anticoagulation could and should be avoided for biological implants.