Abstracts

DO DIFFERENT DEGREES OF LOW-GRADE REJECTION PREDICT LONG-TERM OUTCOMES IN PEDIATRIC HEART TRANSPLANTATION?

Gregory H. Tatum, Steven A. Webber, Division of Pediatric Cardiology, Children’s Hospital of Pittsburgh of UPMC, Pittsburgh, PA, USA

Background and Aims: In 2005, the International Society for Heart and Lung Transplantation proposed to simplify the cardiac allograft rejection grading system by merging mild diffuse rejection (1B) with mild focal rejection (1A) (along with focal moderate, grade II) into a single grade 1. This assumes equivalent prognostic significance of these grades. We hypothesized that recurrent grade 1B rejection is associated with a worse long-term outcome.

Methods: We retrospectively reviewed data on pediatric heart transplant recipients (< 21 years old) managed with tacrolimus based immunosuppression from 10/89-1/02. Patients were included if first year rejection history was benign (all grades <3A) beyond the first six weeks after transplantation and they had at least 4 biopsies performed between 6 weeks and 1 year after transplantation. Patients with at least 80% of endomyocardial biopsies (EMB) between 6 weeks and 1 year with only 0 or 1A rejection were considered minimal rejectors (Group A). Those with >20% 1B on EMB were considered as mild diffuse rejectors (Group B). Outcome measures included any episode of acute late (> 1 year) rejection (≥ 3A), coronary artery disease, re-transplantation, death, or a composite end-point of the presence of any of these outcomes.

Results: Of 106 transplants, 47 fulfilled eligibility criteria (40 Group A, 7 Group B). There was no difference in the incidence of acute late rejection (37.5% vs. 57.1%; p=0.285) or coronary artery disease (22.5% vs. 14.3%; p=0.533) between groups. The incidence of re-transplantation (12.5% vs. 14.3%; p=0.642), death (7.5% vs. 14.3%; p=0.487) or of the composite end-point of any adverse event (52.5% vs. 71.4%; 0.307) also did not reach significance.

Conclusions: Although this single center pilot study did not reveal statistically significant differences between groups, the weak trend to worse long-term outcome in the patients with recurrent 1B rejection has led us to develop a multicenter study. It seems warranted to await further results before abandoning the current ISHLT classification.