Ann Thorac Surg 2001;72:2076
© 2001 The Society of Thoracic Surgeons
Invited commentary
John A. Hawkins, MDa
a Division of Cardiothoracic Surgery, Primary Children’s Medical Center, 100 N Medical Dr, Salt Lake City, UT 84113, USA
e-mail: jhawkins{at}med.utah.edu
This article by Dr Sinzobahamvya and colleagues offers a detailed look at the fate of small diameter valved allografts inserted in the pulmonary position in neonates and infants. Much has been written about allograft conduits in recent years regarding the rapid degeneration and need for replacement of these valved conduits, particularly in neonates and small infants. The authors have demonstrated that conduits in the 8 mm to 10 mm size range degenerate and need replacement more rapidly than those in the 11 mm to 13 mm size range. This was best predicted in their study of z-scores based upon the child’s surface area with valved conduits with z-scores greater than 2 having a freedom from failure rate of about 85% at 5 years, as compared to a freedom from failure at about 25% at 5 years for this with z-scores less than 2.
This study offers better results for freedom from reoperation than I have seen in my own practice with 11 mm to 13 mm valves, and those that have generally been achieved in neonates in other series utilizing cryopreserved valved allografts in this size range. Why is this? One explanation might be more stringent indices for replacement of a conduit, but the authors have appropriately pointed out that they generally replaced the conduit when right ventricular pressure neared systemic levels, regardless of the patient’s symptoms. Another explanation might be the very favorable outcome of valved allografts supplied from one institution that used only cadaver donors and avoided fresh or "homovital" allografts. Or, it is possible that these grafts may elicit less of an immunologic reaction and this may in turn translate into better longevity. We are recognizing that cryopreserved valved allografts do cause an immunologic reaction, particularly in neonates and small infants, but the role immunology plays in the durability of allograft valves is less clear. Certainly the fact that the earliest failure for a valve with a z-score value greater than 2 was supplied by the single institution was 135 months is an amazing feat!
The most important message to obtain from this article is that small valves in small infants fail rapidly, and larger valves (z-score 2 to 3) fail less rapidly in this difficult population group. Although the authors did not see a difference for failure rate for z-scores greater than 2 in infants less than 30 days old, as compared to those older than 30 days, it is nearly impossible to separate similar or linked variables such as small infant size (weight or body surface area) and small conduit size. It is hard to expect much more than 3 or 4 years from a valved conduit in an infant 1 weighing less than 2.5 kilograms, due to the expected rapid growth and weight gain in the first few years of life of a child this size. Caution should also be used in oversizing valves too much. This can necessitate longer ventriculotomies, or may lead to compression from the sternum and contribute to postoperative morbidity. The authors should be commended on excellent results and for demonstrating that more careful sizing utilizing z-scores can contribute to better longevity of the cryopreserved valved allografts in this difficult group of patients.
Related Article
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The fate of small-diameter homografts in the pulmonary position
- Nicodème Sinzobahamvya, Jutta Wetter, Hedwig C. Blaschczok, Mi-Young Cho, Anne Marie Brecher, and Andreas E. Urban
Ann. Thorac. Surg. 2001 72: 2070-2076.
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