Angioplasty, an jee oh PLAS tee, is a technique used to open arteries that have become blocked by deposits of cholesterol, calcium, and other substances. Such deposits are called plaques. Angioplasty is especially important for patients whose coronary arteries have become critically narrowed and who have angina (chest pain that occurs during exertion) or a high risk of heart attack. Angioplasty provides an alternative to surgery.