The basic idea is to improve blood flow to the heart by making the blood vessels wider.
During a PCI procedure, a balloon-tipped catheter is threaded over a guide wire until it reaches the narrowed area (as identified in an angiogram). When in position, the balloon is inflated at high pressure, compressing the obstructing atheromatous plaque and enlarging the inner diameter of blood vessels so that blood flows more readily. This procedure is known as balloon angioplasty.
Angioplasty was introduced in 1979 but “elastic recoil”, where arteries return to their original size following removal of the balloon and “restenosis” the development of scar tissue at the site of balloon inflation, were responsible for re-narrowing of the vessel in 20-50% of patients.
Stents were implanted to prevent elastic recoil and to reduce the chances of the coronary artery re-closing soon after balloon inflation. The stent (a tiny cage of surgical grade stainless steel) surrounds the outside of the balloon. As the balloon is inflated the stent expands and locks into place to form a scaffold.
The balloon is removed, but the stent remains, holding the artery open. All interventional procedures have an element of risk but the chances of a successful outcome in a non-emergency situation are high – over 98%.
Drug eluting stents
Inevitably some injury occurs to the artery during stent placement. This can trigger a healing process where scar tissue collects on the inside of the stent, making the stented vessel narrow again. It is most likely to occur in small vessels, long stents and in people with diabetes.
Drug “eluting” stents have now been developed to stop the growth of the scar tissue.
They use a small amount of immunosuppressive drug loaded on to the stent to prevent vascular smooth muscle cells dividing and growing in number. As vascular cells are a key component of scar tissue, suppressing them in this way reduces scarring significantly within the artery.
Heart bypass surgery
Coronary artery bypass graft operations, also referred to as CABG, involve surgery to harvest a piece of artery or vein from another area of the body where it is not needed (such as the long vein in the leg or an artery in the chest wall). One end of the replacement artery or vein is sewn into the aorta (the large artery leaving the heart) and the other end is attached to the blocked coronary artery just below the blocked area, allowing blood to use this new path to flow freely to the heart.
Deciding whether to have PCI or bypass surgery can be difficult and it needs careful consideration. Drug eluting stent technology means many patients previously unsuitable for stenting can now avoid the more invasive bypass surgery.