Cardiac catheterization is a medical procedure used to further investigate cardiac disease or actually treat a condition of the heart. It involves the insertion of a thin, flexible tube, referred to as a catheter, into an artery in an arm or leg. The catheter is routed to the heart, where your healthcare provider can see the vessels of the heart and note any disease. It is commonly used to investigate atherosclerosis within the arteries of the heart. If stenosis or blockage is noted during cardiac catheterization of the heart, certain procedures can be performed to open the arteries narrowed by atherosclerosis.