Therapeutic opening of a blocked blood vessel. Usually a balloon is inflated near the end of a catheter (seecatheterization) to flatten plaques (seeatherosclerosis) against an artery's wall. Performed on a coronary artery, angioplasty is a less invasive alternative to coronary bypass surgery in the treatment of coronary heart disease. Complications, including embolisms and tearing, are rare and results are excellent, but plaques tend to build up again after the procedure. Angioplasty is also used to expand a severely obstructed heart valve.