Abstract 14567: Detection of Acute Cellular Rejection in Pediatric Heart Transplantation: A Pilot Cardiac Magnetic Resonance Imaging Study

Abstract

Introduction: The diagnosis of significant acute cellular rejection (ACR) after heart transplantation (HT) prompts an immediate change in management and is associated with adverse outcome. Endomyocardial biopsy (EMB) is the gold standard for the detection of ACR but has important limitations. The purpose of this study was to evaluate cardiac magnetic resonance imaging (CMR) as a non-invasive tool to detect ACR in pediatric patients after HT. Methods: In this single centre prospective cohort study, 30 pediatric HT recipients underwent CMR at the time of surveillance EMB. Their CMR results were compared to 14 non-HT pediatric controls. Ventricular volumes and ejection fraction, native T1 times and T2-weighted signal intensities were compared between patients and controls and between patients with (grade 2 R) and without (grade 0 R/1 R) significant ACR according to standard criteria. Extracellular volumes (ECV) and the presence of late gadolinium enhancement (LGE) were compared between the two HT groups. Results: There were no significant demographic differences between the patient groups. Transplant patients were on average 11 ± 6.1 years of age and were 31.5 ± 41.3 months post-transplant. Significant (grade 2 R) ACR was an infrequent event in our population (5/30, 17%). Compared to controls, heart rate (100.3 ± 16.4 bpm) and brain natriuretic peptide (60.8 ± 100.7 ng/L) were significantly elevated post-HT but did not differentiate between grades of ACR. Ventricular volumes, ejection fractions, LGE prevalence, ECVs, native T1 times and T2 signal intensities were not significantly altered by ACR. Conclusions: We describe the myocardial characteristics of pediatric HT recipients by CMR. Although limited by the small number of patients with significant ACR the results of this pilot study suggest that current CMR imaging protocols are insufficient to reliably identify ACR-related changes in pediatric HT.