Non-invasive Prediction of EArly Cardiac rEjection

Acute rejection remains a major cause of morbidity and mortality in pediatric patients after heart transplant. In order to screen for rejection, most centers perform heart catheterizations with endomyocardial biopsies frequently in the first year post transplant and then every 1-2 years thereafter; these biopsies are associated with complications, can cause significant anxiety in patients and family members, and are a significant cost for the healthcare system. This project will evaluate non-invasive methods of detecting rejection using cardiac magnetic resonance imaging and blood testing with a goal to reduce the required number of cardiac catheterizations.

Inclusion Criteria: * Received heart transplant at age \< 21 years old * \> 2 months from transplant * ≥6 years old and ≤ 25 years old and able to undergo cardiac MRI (CMR) * CMR can be scheduled within 5 days from heart biopsy\* * Heart catheterization with biopsy is scheduled "for cause" to confirm suspected AR or Heart catheterization with biopsy is scheduled for surveillance Exclusion Criteria: * No endomyocardial biopsy scheduled * Other illness or disease process that could potentially lead to myocardial edema or fibrosis * Contraindication to CMR with contrast * Previously enrolled in this study, UNLESS previous enrollment was heart biopsy scheduled for surveillance with no suspicion of AR AND final study status was documented as "no AR" AND current enrollment is heart biopsy is scheduled "for cause" to confirm suspected AR * Multiple transplanted organs * Requires anesthesia for CMR