Heightened Immune Response and Increased Risk of Infections in Pediatric Fontan Patients after Heart Transplantation

Abstract

Infectious complications are a major cause of morbidity & mortality after heart transplantation (HT). Patients who have undergone Fontan palliation may have a higher susceptibility to post HT infections given thymectomy in infancy and known depletions of T-cell subsets. This was a single-center, retrospective cohort analysis of pediatric patients undergoing HT for dilated cardiomyopathy (DCM) or failing Fontan physiology, who underwent post HT induction with anti-thymoglobulin (ATG). Repeat HTs and multi organ transplants were excluded. The primary endpoint was infection in the first 180 days post HT, defined as 1) positive blood, urine, or respiratory culture; 2) positive viral PCR (excluding CMV and EBV); 3) skin or wound infection; or 4) culture-negative infection if a full antibiotic course (≥ 5 days) was completed. Secondary endpoints included sensitivity to ATG as defined by 1) absolute lymphocyte (ALC) and CD3 counts after 5 doses; 2) the incidence of post transplant lymphoproliferative disorder (PTLD); and 3) rejection (>/= Grade 2R ACR or pAMR2) in the first 180 days post HT. From 1/2014 to 9/2019, 63 patients (30 Fontan, 33 DCM) underwent HT at a median of 15.4 (IQR 10.8, 20.1) and 11.7 (IQR 1.4, 13.6) years, respectively. The median total ATG received was 7.5 (IQR 6.7, 8.2) mg/kg vs 7.2 (IQR 4.7, 9.2) mg/kg (p=NS), respectively. The median CD3 [9 (IQR 3,14) vs 12 (IQR 6, 26); p=0.04, Figure 1A] and lymphocyte counts [172 (IQR 98, 354) vs 427 (IQR 205, 662); p=0.02] after ATG were lower in Fontan vs DCM patients. 28 patients (41%) developed at least one infection within 180 days after HT, with a higher rate of infection in Fontan patients (60% vs 24%, p=0.005; Figure 1B). There was no difference in the incidence of PTLD (10% vs 0%; p=0.1) or rejection (17% vs 27%; p=0.31) between Fontan vs DCM patients, respectively. Compared to DCM patients, Fontan patients have a more pronounced suppression of CD3 counts after induction, as well as a higher risk of infection.