Atherosclerosis, a buildup of fatty material called plaque in the arteries, can narrow the vessels that supply the heart with blood. If an artery becomes completely blocked, a heart attack can result. Stents, which are mesh tubes, hold the artery open and prevent it from becoming completely blocked. Surgeons often place stents in conjunction with angioplasty, a procedure that opens an artery and improves blood flow. Stents accompany 70 percent of angioplasties, the Encyclopedia of Surgery reports 1.

Blood Clots

Blood clots develop in 1 to 2 percent of patients after stent placement, the National Heart Lung and Blood Institute reports 2. Blood clots can block a blood vessel, often causing a heart attack, or can lead to stroke. The risk of developing blood clots is highest in the first few months after stent placement. Stents coated with medications that keep the artery open cause a higher risk of blood clotting. Patients may need to take anticoagulant—or anti-clotting—medications for up to a year after stent placement to prevent blood clot formation.

Restenosis

Collagen deposits in a blood vessel can cause restenosis after stent surgery. Early restenosis occurs in fewer than 1 percent of cases, whereas late restenosis occurs between 5 to 10 percent of the time when a patient receives a medication-coated stent, the Merck Manual for Healthcare Professionals reports 3.

Infection

Infection can occur after any invasive procedure, including stent placement. Fever and chest pain within the first few weeks after surgery warrant immediate workup for infection, because infection carries a 40 percent mortality, or death rate, reports Dr. Beat A. Kauffmann of the Department of Cardiology at the University of Basel, Switzerland, in the August 20, 2010 issue of “Swiss Medical Weekly.” Pain, swelling, pus drainage or redness at the puncture site also require immediate medical evaluation.

Heart or Vessel Damage

Heart or blood vessels may be damaged during stent placement, the Encyclopedia of Surgery reports 1. In rare cases, sudden cardiac death occurs during angioplasty and stent placement. Around 10 percent of patients have chest pain within 48 hours after angioplasty and stent placement, possibly because of a small tear in the inner layer of the blood vessel, reports Dr. Julian Aroesty of Harvard Medical School on UpToDate 5.