Abstract 10380: Differences in Cardiac Magnetic Resonance Native T1 Values Demonstrate Utility in Identifying Acute Cellular Rejection and Assessing Graft Health

Abstract

Introduction: Cardiac Magnetic Resonance (CMR) is an emerging tool for cardiac graft assessment in heart transplant recipients, with native T1 mapping directed at identifying both rejection and graft fibrosis to predict and guide management of graft dysfunction. Hypothesis: CMR native T1 values may identify acute rejection, predict graft dysfunction, and in secondary analysis, correlate with fibrosis percentage from right ventricle (RV) endomyocardial biopsy (EMB). Methods: Pediatric subjects (n=34, age 12.4±4.9 y, graft age 5.4±4.3 y, LVEF 62.9±5.6%) underwent simultaneous EMB and 1.5T CMR with breath-held T1 mapping via Modified Look-Locker Inversion recovery in 8 short-axis slices, from which global mean and peak native T1 values were quantified. EMB analyzed for histopathological fibrosis% using digital analysis of Maisson’s trichrome stained slides. Patients were stratified into three groups by decision to treat: acute rejection with new treatment initiated, ongoing treatment modified, or no change in treatment. In patients without acute rejection, linear regression was used to compare T1 values with clinical markers of right atrial (RA) mean pressure and brain natriuretic peptide (BNP). Results: Mean T1 values were higher in patients with acute rejection compared to those without, with stratified groups demonstrating a monotonic trend; peak T1 values trended towards significance. In patients without acute rejection, peak T1 values correlated with BNP (r=0.53, p=0.004) and RA mean pressure (r=0.39, p=0.046). Fibrosis% from random RV EMB did not correlate with native T1 values or clinical markers of graft dysfunction. Conclusion: In pediatric heart transplant patients, T1 values from comprehensive CMR identified acute rejection requiring initiation of treatment and graft dysfunction, with regional analysis key to capturing correlation with clinical markers. CMR shows promise as an important tool for evaluation of graft health in children.