Right ventricle-to-pulmonary artery conduit longevity: Is it related to allograft size?

Background. Cryopreserved valved allografts are routinely oversized to account for somatic growth in children requiring right ventricle-to-pulmonary artery (RVPA) continuity. The objective of this study is to determine the effect of oversizing on conduit longevity. Methods. We reviewed the records of all patients undergoing RV-PA cryopreserved valved allograft placement from 1988 to 2006 for diagnosis, age, allograft type, time to valved conduit explant, and indication for surgery. Conduit size at the time of insertion was compared with pulmonary valve size normalized for body surface area (z score). Multivariate Cox regression models with cluster analysis were constructed to assess risk of allograft oversizing for conduit failure. Kaplan-Meier analysis was used to obtain median freedom from explantation time. Results. A total of 140 cryopreserved valved allografts (z score, 1.8 +/- 1.3; range, -1.5 to 4.9) were implanted in 99 patients ( median age, 5.6 years). Reoperation was required in 66 (67%) of 99 patients during the study period. Modeling z scores as a dichotomous variable revealed that risk of allograft explantation increases 113% when allografts with z scores of 2.7 or higher are used compared with those with z scores of less than 2.7 ( p < 0.01). Median adjusted freedom from explantation for this same grouping was 4.9 years versus 9.4 years. The presence of branch pulmonary artery stenosis shortens the conduit life (p < 0.001), whereas insertion of a pulmonary allograft may extend the conduit life (p = 0.13). Conclusions. Cryopreserved valved allograft oversizing (z score >= 2.7) in the pulmonary position results in decreased longevity in children. Presence of branch pulmonary artery stenosis is also associated with earlier conduit explantation.