Abstract 4144738: Change in Valve Function During Pediatric Heart Transplant Graft Rejection May Shed Light on Immunosuppressive Strategies for Partial Heart Transplantation

Introduction: Partial heart transplant (HT), the transplantation of living/growing heart valve implants, has emerged as a novel solution for children with complex CHD and semilunar valve dysfunction. Management of immune suppression following partial HT is unclear, and may be aided by understanding how valve function changes during full HT graft rejection. Aims: To compare semilunar and atrioventricular (AV) valvular function before and during biopsy-proven rejection by echocardiogram imaging in pediatric HT recipients. Methods: Single institution retrospective study including all pediatric HT recipients during 2005-2023 with biopsy diagnosed rejection, a preceding biopsy with no rejection (baseline), and available echo within 24 hours of each biopsy. All echos were reviewed by a pediatric imaging cardiologist to qualitatively grade valvular and ventricular function. Change in valvar/ventricular function was assessed by McNemar’s and Fischer’s exact tests. Results: The cohort comprised 87 patients (43.7% female, mean age 14.2 years [SD +/-6.5], 60% with acute cellular rejection and 40% with antibody mediated rejection, median time between baseline and rejection diagnostic biopsy/echo pairs 6.5 months [SD +/-3.9]). At baseline, 99% of patients had no/mildly depressed left and right ventricular systolic function. During rejection 18%(17) patients had progressed to moderate or greater LV dysfunction and 15%(13) had moderate or greater RV dysfunction (p-value <0.001 for both). There were no instances of aortic, pulmonary, mitral, or tricuspid stenosis. No patients had more than trivial aortic regurgitation (AR) at baseline or during rejection. At baseline 1%(1) of patients had mild PR versus 6%(5) during rejection (p=0.103). The proportion of those with mild or greater MR increased from 17% at baseline to 39% during rejection (p=0.0003). Worse MR during rejection was seen in a higher proportion of those who developed > mild LV dysfunction during rejection compared to those who did not (82% vs. 22%, p<0.001). Those with mild or more TR increased from 39% to 52% during rejection (p=0.068). Conclusion: There was no significant semilunar valve dysfunction during graft rejection in pediatric HT recipients using contemporary immune suppression. This suggests that less immunosuppression may be sufficient to preserve the longevity of semilunar valve transplants. Mitral valve dysfunction was worse during rejection, but was related to LV dysfunction and warrants further study.