Abnormal Cardiac Magnetic Resonance Imaging Mapping Parameters in Pediatric Heart Transplant Patients with Elevated...

Heart transplant (HT) rejection surveillance is rapidly evolving with evidence supporting use of donor-derived cellfree DNA (ddcfDNA) with its high negative predictive value and use of cardiac magnetic resonance (CMR). Both modalities are imperfect in diagnosing biopsy proven rejection, however, combining them may improve diagnostic power. Our study goal is to characterize multiparametric CMR trends between pediatric HT patients (PHT) with high versus low ddcfDNA. Single center retrospective study of PHT who had clinically indicated multiparametric CMR (biventricular volumes and ejection fraction (EF), T2 mapping, T1 mapping with extracellular volume fraction (ECV) and ddcfDNA within 30 days; corresponding EMB was not always performed as per institutional clinical protocol. Demographics and CMR variables were compared between ddcfDNA of ≥ 0.16% (high group) and < 0.16% (low group). 68 PHT (14 high group, 54 low group) were included. The high group was significantly older, with longer time between CMR and HT, had longer time between CMR and ddcfDNA, had more frequent CMR indication of clinical concern and had history of CAV or moderate severe rejection. No statistical difference in CMR derived ventricular volumes or function was noted between groups. There were significant differences in multiparametric mapping with high ddcfDNA group showing higher global T1 (1086 [1050, 1118] vs. 1029 [1002, 1075] ms; p = 0.01), peak segmental T1 (1163 [1140, 1220] vs. 1121 [1056, 1175] ms; p = 0.04), global T2 (52 [50, 55] vs. 48 [46, 51] ms; p = 0.008), and peak segmental T2 (58 [54, 60] vs. 53 [51, 59] ms; p = 0.04) compared to the low ddcfDNA group respectively. Multiparametric CMR suggests graft structure differences between high and low ddcfDNA PHT. Studies on larger cohorts with wider ddcfDNA ranges can help understand the combined role of CMR and ddcfDNA in improving surveillance.