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 which may reduce or eliminate angina. PCI can restore blood flow in the event of a heart attack.

You will be asked not to eat or drink after midnight the evening before the procedure.
You are not given a general anaesthetic but may have some medication to relax you if needed. Local anaesthetic is put into an area of skin to the side of your groin. A needle and then tube are fed into an artery here and advanced though the blood vessels to the heart. You can’t feel this. Dye is injected so that the heart and blood vessels can be seen on X-ray. X-rays and measurements are then taken giving the doctors information about the state of your heart and the exact nature of any narrowed blood vessels.
After the catheter is placed in the artery with a blockage, one of the following options may be considered:

Balloon angioplasty: 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. 

Stent: a stent is a small stainless steel mesh tube that behaves like scaffolding and gives your 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 on top of the balloon 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.