590 Long-Term Outcome of Pediatric Heart Transplant Patients with Incidental Subclinical Cellular Rejection during Annual Study

Purpose: Positive biopsies (Bx+) have been found late in children during their annual study and have been considered subclinical rejection. This study retrospectively evaluated the long-term outcome of patients (pts) who had one or more Bx+ during their annual study compared to those biopsy negative (Bx-). Methods and Materials: All children who had a heart transplant (tx) at our institution were included except those followed elsewhere, or died or had a recent tx. Bx + was defined as either a 3A or 2R bx found on annual catheterization on/after the 3rd year. Outcome variables included graft loss (GL), death, retx, cellular/vascular causes (e.g. allograft vasculopathy, chronic graft dysfunction, acute rejection), and other causes (e.g. sepsis, lymphoma). Variables were compared using chi-square. Freedom from GL was evaluated using Kaplan-Meier analysis. Student's t-test was used to evaluate the differences between the groups. A p-value < 0.05 was considered significant. (Graph Presented ) Results: 267 pts met inclusion criteria. (Bx-: 184, Bx+: 82, time of Bx+: 3-18 years post-tx). There was no statistical difference in tx age or follow-up. Bx+ pts had a higher incidence of GL (p=0.003), a higher death rate (p=0.038), and occurred from cellular/vascular causes (p=0.002). Other causes and retx were not significantly different. The bx+group had a lower rate of survival (0.33±0.09 vs. 0.63 ± 0.05, p = 0.05) at 23 yrs compared to the bx - group. Conclusions: Pts who have incidental 3A/2R biopsies had a poorer longterm outcome compared to those who were Bx-. This group suffered from a significantly higher incidence of cellular or vascular disease as the cause of graft loss. The cause of this difference is unclear.