Cardiac catheterization. Overview. Cardiac catheterization (kath-uh-tur-ih-ZAY-shun) is a procedure used to diagnose and treat cardiovascular conditions. During cardiac catheterization, a long thin tube called a catheter is inserted in an artery or vein in your groin, neck or arm and threaded through your blood vessels to your heart. Using this catheter, doctors can then do diagnostic tests as part of a cardiac catheterization.