Cardiac catheterization is the procedure in which a doctor guides a thin plastic tube or catheter through an artery or vein in the arm or leg and into the heart and the coronary arteries in the heart. This test can measure blood pressure and how much oxygen is in the blood, and provide other information about the pumping ability of the heart muscle, or for treatment. When a catheter is used to inject dye into the coronary arteries, this is termed coronary angiography or coronary arteriography. If a catheter has a balloon on the tip, the procedure known as percutaneous transluminal coronary angioplasty (P.T.C.A.) can be done. Catheterization can also be performed on infants and children to examine or treat congenital cardiac defects.