332.9: Decision making in an adolescent requiring emergent heart transplant – Is HLA matching relevant?

Abstract

Background: A 17-year old boy with Ebstein’s anomaly of tricuspid valve, severe biventricular dysfunction and class IV heart failure was admitted for pre-heart transplant evaluation (HT). Three days later, he had sudden cardiac arrest and revived with CPR and placed on VA ECMO. Attempts at ECMO wean were unsuccessful due to RV dysfunction. Pre-transplant work up showed acute kidney injury (AKI) and otherwise he was deemed an eligible recipient for emergent heart transplantation. Luminex® single antigen bead test was negative for Class I and Class II HLA antibodies. On ECMO day 5, a suitable donor was available. HLA typing of donor and recipient revealed 4 out 6 mismatch. Luminex DSA cross match was negative. Two doses of intravenous Basliximab (20 mg each) were used for induction therapy. Post operative graft function was excellent, and surveillance endomyocardial biopsies done on day 7 and day 21 were negative (ISHLT Grade 0 ACR; pAMR0; C4d and CD68 negative on IHC). He was discharged home on post-operative day 29 with oral Tacrolimus, Mycophenolate Mofetil and low dose prednisolone. He continues to do very well on follow up at 1 year. Luminex DSA continues to be negative for Class I and Class II antibodies. Discussion: Children with heart failure bridged to mechanical circulatory support are at high risk for early graft rejection after HT. Emerging crossmatch methods and HLA typing are crucial to improve organ allocation and achieve better match to recipients of HT. Extensive HLA antigen polymorphism, donor shortage and logistics and ischemia time are some of the limiting factors to derive better HLA compatability. HLA matching increases graft survival and reduce the incidence of graft rejection. HLA-DR mismatch is independently associated with ACR at 1 year and predicts long term survival in HT. Graft survival increased with fewer HLA-DR mismatches [0–1 vs. 2 mismatches: risk ratio (RR) = 1.09 (95% confidence interval (CI): 1.01–1.19; P = 0.04)]. Although our patient has several risk factors (pre-transplant ECMO, emergent listing, complicated hospital course) for successful outcome, having fewer HLA DR mismatch and negative DSA at 1 year follow up is encouraging.