Cardiac catheterization (or heart catheterization) is a specialized test that provides information about certain heart conditions that cannot be obtained with any other tests. The test is performed while your child is under deep sedation. During the test the pediatric cardiologist advances very thin plastic tubes (called catheters) into the circulation through a vein or artery at the top of your child’s leg or arm. The catheters directly measure blood pressures and oxygen levels within the circulation. Then, the pediatric cardiologist injects medicine (called contrast) within the catheters. This produces X ray movies of the heart called angiograms. All of this information can be very important to decide how serious your child’s heart problem is, and whether further treatment is needed. After the test is completed your child is transferred to a recovery area and is usually discharged home later that same day.