A stent is a tiny mesh tube that looks like a small spring. The stent is permanently inserted in the area where your artery has narrowed to keep it open. Some stents are "coated" with medication to help prevent the artery from closing again. Stents are used in most angioplasties except when an artery is too small for a stent to fit.
Sometimes even with a stent in place, an artery can reclose. This requires another angioplasty or bypass surgery to correct the problem.