The overall purpose of this protocol is to identify subacute sepsis-associated cardiac disease in pediatric patients with cancer by CMR and evaluate the CMR findings during their follow-up. This will help inform heart failure management decision making. Evidence of dysfunction or elevated T2 values may inform adjustment of afterload reduction and beta blocker administration, and elevated ECV findings will suggest the need for increased surveillance for diastolic dysfunction. Primary Objectives: (Feasibility Phase) To determine the feasibility of cardiac MRI without anesthesia in the immediate post-sepsis period in children with cancer. CMR scanning will be completed within 10 days of presentation - this will allow us to ensure that possible hemodynamic or respiratory instability and renal dysfunction has resolved prior to transport to the MRI scanner during the most acute phase of illness. (Completion Phase) To estimate the frequency of subacute sepsis-associated cardiac disease, including myocardial inflammation and dysfunction, in the post-acute phase (within 10 days of presentation) of severe sepsis in children with cancer