Overall Research Strategy of this protocol is to refine and validate noninvasive CMR imaging sequences with invasive hemodynamic and pathology results to create a comprehensive, noninvasive, radiation-reduced regimen for pediatric cardiomyopathy and cardiac transplant assessment. We were the first to perform MR-guided cardiac catheterization in US children, and have accumulated the largest US experience, having performed over 75 procedures to date. Our unique experience puts us in strong position to leverage this technology to improve care of children with cardiomyopathy and transplant. Using an integrated approach, we will simultaneously (1) validate imaging measures of cardiac edema and fibrosis by correlating T1 and T2 map images with endomyocardial biopsy (EMB) results in Aim 1; (2) overlay T1, T2 map images into our x-ray system to display hotspots of T1 and T2 abnormalities to guide EMB in Aim 2; and (3) obtain radiation-free hemodynamic data in a highly vulnerable pediatric population by using CMR to guide catheter manipulation in the ICMR suite in Aim 3. Age and diagnosis-matched historical controls will be identified from the last 10 years at Children's National as a control population for specific purposes of comparing (1) EMB yield without image overlay and (2) Radiation exposure during X-ray guided right heart catheterization. Identical information will be obtained and stored in the same 45CFR compliant database. Historical controls will be identified from the cardiac catheterization database by searching for age and diagnosis. A waiver of consent will be applicable here, as it would be inconvenient, insensitive and not feasible to consent families who have already undergone treatment.