Cardiac Magnetic Resonance in Heart Transplant Recipients: Histological, Clinical and Cell-Free DNA Validation.

Aims: Cardiac magnetic resonance (CMR) presents a promising non-invasive method for evaluating acute rejection in heart transplant recipients. As indicators of myocardial injury, T1 and T2 mapping values are crucial for comprehending rejection patterns in heart transplants. This study aims to define CMR T1 and T2 mapping values in heart transplant patients both with and without acute rejection.

Methods and results: In this blinded prospective study, we analyzed CMR data from 244 scans of 58 pediatric and adult heart transplant recipients, 1-24 months post-transplant. Rejection status was defined by endomyocardial biopsy, clinical data, and donor-derived cell-free DNA (dd-cfDNA). Over the 24 months post-transplant, global T1 and T2 values decreased significantly (T1: β = -9.1/log(month), p < 0.001; T2: β = -0.5/log(month), p < 0.001) demonstrating the gradual recovery from transplant-related myocardial injury. During acute rejection, T1 values significantly increased compared to rejection-free studies in both children (estimates at one month post-transplant 1188 ms [95% CI: 1161-1215] vs. 1079 [95% CI: 1061-1097], p < 0.001) and adults (1087 ms [95% CI: 1045-1129] vs. 1016 [95% CI: 1005-1027], p = 0.007). T1 and T2 values were positively associated with dd-cfDNA (p < 0.001 and p = 0.014, respectively), and T2 values with worse left ventricular global longitudinal strain (p < 0.001).

Conclusion: We provide essential T1 and T2 mapping values across cardiac segments, as well as left ventricular myocardial strain, both with and without acute rejection. These findings establish a reliable foundation for non-invasive heart transplant rejection screening.