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Original Articles: Cardiovascular

Invited commentary

Department of Cardiovascular Surgery, Clinic for Cardiovascular Surgery, University of Berne, Freiburgstrasse, Berne CH-3010, Switzerland

(Email: thierry.carrel{at}insel.ch; florian.schoenhoff{at}insel.ch).

Favorable early and mid-term outcomes after corrective congenital surgery (including reconstruction of the right ventricular outflow tract) have led to an increasing demand for right ventricular-pulmonary artery (RV-PA) conduits in children, adolescents, and even in adult patients. Unfortunately there still is no ideal conduit that fulfills all the expectations (eg, autologous material, unrestricted and immediate availabilty, growth potential, resistance to infection, and, last but not least, excellent long-term durability and low rate of structural degeneration).

Because the successful introduction of cryopreservation in the 1980s, pulmonary homografts have been considered as the conduit of choice by a large number of surgeons. However, the expanding use for homografts has led to an increasing mismatch between demand and supply and has made availaibility a limiting factor for the use of homografts, mostly in small sizes. With the advent of the Contegra bovine jugular vein graft (Medtronic Inc, Minneapolis, MN) and the new generation of Shelhigh pulmonic porcine xenograft (NR-4000PA, Shelhigh Inc, Union, NJ) there was reasonable hope to overcome this lack of homograft availability. However, despite favorable immediate hemodynamic results, these new grafts raised several questions regarding durability.

Kim and co-workers [1] report their experience with 81 Shelhigh pulmonic xenografts (median size, 18 mm) (Shelhigh Inc), mainly in tetralogy of Fallot patients who required RV-PA conduit implantation.

This article has several weaknesses that make general statements regarding the performance of the conduit difficult if not questionable. Follow-up is rather short with a median of 8 months, but freedom from reoperation is only 58% in the group who received larger conduits (>18 mm) and drops to 33% in patients with small-sized conduits (12 mm).

The primary mechanisms of RV-PA conduit failure generally include stenosis, especially at the level of the distal anastomosis, multi-level stenosis, intimal peel, embolism, thrombosis, and calcification with or without valvular dysfunction.

Excessive intimal peel is a major problem, especially with the Shelhigh pulmonic graft. Although the authors do not comment, it seems at least from previous publications that some degree of anticoagulation (ie, platelet inhibitor or coumadin) can be recommended.

In neonates and infants, immunologic mechanisms should not be overlooked. In some individuals, a rise in B cells to 150% of the normal value may be observed 3 to 6 months postoperatively and is associated with T-lymphocyte activation, CD69+, and CD71+ cells. Cellular remnants in the xenograft may be responsible for such reactions. Another important issue in the younger age group is the differentiation between effective premature conduit degeneration and failure due to normal somatic growth.

An additional important question remains unanswered by this article. How can the performance between different conduits be compared? To really allow definitive statements about conduit performance requires a comparison between similar patient populations with the same congenital defect, same age group, and similar RV-PA pressure ratio. Primary procedures and reoperations should be equally distributed. It is not surprising that a conduit used to replace the pulmonary valve in a Ross procedure will probably perform better than a conduit implanted in a patient with pulmonary atresia or severe pulmonary hypertension.

Finally, although it does not affect the present study, it should be noted that all Shelhigh products, including the Shelhigh pulmonic NR-4000 PA, were seized by the Food and Drug Administration in May 2007 [2].

	References

Top References

 

1. Kim W-H, Min SK, Choi CH, et al. Follow-up of Shelhigh porcine pulmonic valve conduits Ann Thorac Surg 2007;84:2047-2051.[Abstract/Free Full Text]
2. FDA preliminary public health notification: possible contamination of heart valves and valved conduits, annuloplasty rings, surgical grafts, meshes and other devices manufactured by Shelhigh, Inc. Available at: www.fda.gov/cdrh/safety/041907-shelhigh.html. Accessed May 18, 2007.

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Thierry Carrel Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Carrel, T. Articles by Schoenhoff, F. Search for Related Content PubMed PubMed Citation Articles by Carrel, T. Articles by Schoenhoff, F. Related Collections Congenital - cyanotic Related Article