An angioplasty (not surgery) is the introduction of a cath up through the vessels into the coronary (heart) vessels. The procedure is to expand the area of interest with a balloon and then insert a stent to hold the artery open. The individual is awake during the entire procedure but medicated, and usually the vessel hasn't shrunk, but there is a plague formation that narrows the opening.
The American Academy of Cardiologists and American Heart Association have guidelines to follow, and that is not stent any artery that is less than 70% blocked. There are exceptions and that could be to stent if medication does not control angina (chest pain).
There has been a trail study done a year or so ago that indicates people with coronary artery disease (blocked, narrow) and are treated medically or with a stent or open heart surgery do have an an increase in longivity. I have a totally blocked LAD and a 70% blocked circumflex and for the last 4 years been treated with medication and feel very well. Bottom line if pain can be controlled, there is no need to angioplasy and stent.
The trial study is the COURAGE study. You can google COURAGE study for more information. Hope this helps you.