In angioplasty procedures, a balloon is fed through a catheter and used to prop open an artery that has become narrowed or blocked. In cases where stenting is appropriate, a stent mounted on a balloon is inserted and inflation of the balloon expands the stent against the blocked artery wall to hold the vessel open. The balloon is then deflated and the catheter is withdrawn. Stent treatment of arteries holds them open and improves blood flow to the heart. In cases where post-dilatation is needed, a high-pressure balloon is inflated inside a stent to help better place the stent against the vessel wall. More than two million balloon angioplasty procedures are performed per year globally, including nearly 1.3 million procedures annually in the United States.