Cardiac Catheterization A cardiac catheterization is a procedure, which involves insertion of a long, thin, flexible tube, called a catheter, into the heart. The catheter is inserted into a vein and/or artery, usually through the groin. Under the visualization of special x-ray (fluoroscopy), the catheter is advanced toward the heart. This enables the cardiologist to measure pressures and oxygen levels within the different areas of the heart. During the catheterization, special "moving" pictures are obtained after dye is injected through the catheter into a specific area. These pictures are called angiograms. These moving pictures provide valuable information regarding diagnosis and possible catheter treatment (intervention).