an operation for enlarging the narrowed lumen of a coronary artery by inflating and withdrawing through the stenotic region a balloon on the tip of an angiographic catheter.PTCA is a minimally invasive surgical procedure for the treatment of coronary atherosclerosis. A balloon-tipped catheter is inserted percutaneously into the arterial circulation, advanced to the aortic root, and directed with a flexible guide wire to the site of coronary stenosis. Having been positioned within the narrowed arterial segment, the balloon is inflated so as to stretch the lumen, fracture the obstructing plaque, or both. Balloon angioplasty is considered successful when there is more than a 20% increase in the caliber of the stenotic artery and restoration of at least 50% of normal patency, without acute complications. The procedure has approximately a 90% immediate success rate. It offers advantages in symptom improvement and exercise tolerance when compared with medical therapy, particularly in the short term, and is less hazardous and has a shorter recovery period than coronary artery bypass grafting (CABG). Operative mortality is about 2%. There is a 1-3% risk of nonfatal acute myocardial infarction during the procedure and a 1-3% risk that emergency CABG will be required. Hence, the procedure is contraindicated unless a coronary bypass surgical team is immediately available. It is also contraindicated in people without demonstrated significant vascular obstruction, as well as in those with severe multivessel disease or more than 50% stenosis of the left main coronary artery. Angioplasty performed within 2 hours after onset of pain in acute myocardial infarction yields a lower mortality rate and lower rates of nonfatal reinfarction and hemorrhagic stroke than thrombolytic therapy. Despite the advantages of PTCA, 30-50% of patients require repeat balloon angioplasty or CABG for restenosis within 6 months. Insertion of a stainless steel stent at the time of balloon angioplasty to maintain arterial patency has improved initial success and reduced the 6-month restenosis rate. Paclitaxel- and sirolimus-eluting stents further reduce the risk of restenosis.