Factors in the early failure of cryopreserved homograft pulmonary valves in children: preserved immunogenicity?

METHODS: Between 1990 and 1995, 48 homograft valves (15 aortic and 33 pulmonary), cryopreserved on-site, were implanted to reconstruct the right ventricular outflow tracts in 44 children (mean age 6.2 +/- 6.0 years; range 3 days to 20.2 years). Blinded serial echocardiographic follow-up evaluation was performed for all 45 valves in the 41 survivors.
RESULTS: Four homograft valves were replaced because of pulmonary insufficiency (3) or stenosis and insufficiency (1). Freedom from reoperation was 90% (70% interval, 84% to 97%) at 50 months. During the follow-up period 15 valves developed progressive pulmonary insufficiency of at least two grades. Three valves developed transvalvular gradients of > or = 50 mm Hg, and one of these valves was also insufficient. The freedom from echocardiographic failure (two or more grades of pulmonary regurgitation or > or = 50 mm Hg gradient) was 44% at 50 months (70% confidence interval, 32% to 55%). Young age (p = 0.03), low operative weight (p = 0.04), small graft size (p = 0.04), and homograft retrieval-to-cryopreservation time of less than 24 hours (p = 0.02) were significantly associated with failure. The type of donor valve (pulmonic or aortic), donor age, and blood group mismatch were not associated with failure, although blood group mismatch approached significance (p = 0.05).
CONCLUSIONS: Homografts function well as conduits between the pulmonary ventricle and pulmonary arteries if long-term valve competency is not crucial. However, many rapidly become insufficient. This has important implications for the choice of a valve if the indication for valve replacement is to protect a ventricle failing due to pulmonary insufficiency. Short periods between homograft retrieval and cryopreservation enhance viability and antigenicity. This may suggest an immunologic basis for the failure.