Percutaneous coronary intervention (PCI), or angioplasty, is a procedure designed to reduce or remove blockages in the coronary arteries (arteries supplying the heart with oxygen). The purpose of a PCI is to restore blood flow to the coronary arteries and ensure the heart is adequately supplied with oxygen. This may reduce or eliminate angina and can restore blood flow in the event of a heart attack.
During this procedure, a specially designed catheter with a small balloon tip is guided to the point of narrowing in the artery. Once in place, the balloon is inflated to open the artery and stretch the artery to increase blood flow to the heart. 

A stent, a small stainless steel mesh tube, can also be inserted at this time to function as scaffolding and give a coronary artery support. A balloon catheter is used to insert the stent into the narrowed coronary artery. Once in place, the balloon is inflated and the stent expands to the size of the artery and holds it open. The balloon is then deflated and removed, and the stent stays in place permanently.