How much should the artery be blocked before a stent is put in?

The amount of blockage in a coronary artery is only one factor that determines whether or not opening the artery with angioplasty and a stent is needed. For example, someone who has a totally blocked artery but has no chest pain or other heart symptoms does not necessarily need a stent. However, the ideal treatment for a heart attack (myocardial infarction) caused by a blood clot suddenly forming on a partially blocked artery is angioplasty with stent placement.