Angiotensin Converting Enzyme Inhibitors During Cardiopulmonary Bypass in Infants and Children

Inclusion Criteria: * Infants or children (newborn to 17 years of age) undergoing cardiopulmonary bypass for elective surgical correction of a congenital heart defect. * Patients must be taking an ACE inhibitor prior to their operation Exclusion Criteria: * Patients in which discontinuing ACEIs is deemed unsafe by their primary cardiologist * Any condition rendering the subjects legal guardian unable to understand the nature, scope, and possible consequences of the study. * Pregnancy as ruled out by standard of care screening procedures. * Individuals whose weight is less than 3.5 kg at the time of enrollment. * Inability to comply with the protocol. ie. Children in whom it is deemed unsafe to have the extra blood draws, and children who are thought to be noncompliant with their medications.