Biodegradable coronary stents
Biodegradable coronary stents are a new variety of stents being used in coronary arteries. Coronary arteries are the blood vessels which supply oxygenated blood to the heart. Blockages can develop in these blood vessels as age advances due to various disease processes. A critical blockage in the coronary artery is often removed by a procedure known as balloon angioplasty. Once the vessel is opened by balloon angioplasty a scaffolding known as a coronary stent is placed within the artery to prevent reclosure and to maintain a good vessel lumen. Currently metallic stents with or without a drug coated polymer are being used for this purpose. Coronary stents are prone for thrombosis or clotting of blood within the lumen causing obstruction of flow. Metallic stents also alter the geometry of the vessel by straitening out its natural curves and may obstruct side branches. Though drug coated (drug eluting stents) have reduced the chance of restenosis (repeat narrowing) of the vessel after balloon angioplasty, they have a higher rate of thrombosis. Moreover the polymer may irritate the vessel wall, cause dysfunction of the endothelium (inner covering of the blood vessel) and cause chronic inflammation at the stent site. Multiple stents can also cause difficulty during a future coronary bypass graft surgery and potentially interfere with imaging technologies like magnetic resonance imaging and multi slice computed tomography. To circumvent these problems new stents with bioresorbable scaffolds are being evaluated. The scaffolding of these new generation biodegradable coronary stents get bio absorbed after a variable period of time so that what remains is only the native vessel with good endothelial function and natural vessel curves. Poly lactic acid is one of the polymers being evaluated for bioabsorbable stents. Poly lactic acid biodegradable coronary stents have been shown to hold up to 1000 mm Hg of crush pressure and is completely degraded by about nine months.