Project Summary: Children with cardiomyopathy from any cause (genetic, congenital heart disease or myocarditis) require extensive evaluation, including endomyocardial biopsy (EMB), hemodynamic cardiac catheterization, and angiography guided by x-ray, in preparation for, and as routine surveillance following, cardiac transplantation. These invasive tests are the gold standard for determining suitability for transplant and for detection of complications of heart transplant, but also carry risks of invasive procedures and radiation exposure. New cardiac magnetic resonance (CMR) imaging methods called parametric mapping images have emerged to both detect and quantify fibrosis (T1 mapping) and edema (T2 mapping) within cardiac muscle. Preliminary data shows promise in detection transplant rejection and extent of preclinical transplant failure noninvasively in adult pre/post transplant patients. In addition, we have published our experience in using CMR to guide radiation-free hemodynamic catheterization in children and guide radiation- reduced cardiac interventions in the x-ray suite in children. We are well-positioned to accomplish our overarching goal, which is to create a lower risk, radiation- reduced regimen for cardiac assessment in pediatric pre/post transplant patients using CMR imaging that correlates with and predicts invasive testing results (Aim #1), guides invasive EMB with better soft-tissue visualization (Aim #2) and reduces radiation exposure by guiding hemodynamic catheterization assessment (Aim #3). We believe that all patients with cardiomyopathy and heart failure may benefit from completion of this project.