|
HowToPreventHeartDisease.com |
||||||||||||||||||||||||
 |
 |
|
||||||||||||||||||||||
|
Different Kinds of Heart Stents Coronary angioplasty is a procedure used to treat coronary heart disease and angina. It is also used as emergency treatment for people who have had a heart attack. Angioplasty helps improve blood supply to the heart muscle by widening narrowed or obstructed arteries. Frequently though not necessarily, a small tube called stent is inserted during the procedure to ensure the vessel remains open. The stents employed are usually made of metal mesh and are commonly called heart stents, but they are also referred to as cardiac stents or coronary stents. During the first angioplasty performed in 1997 at the University Hospital in Zurich, doctor used small plastic tubing with expandable balloons (balloon catheters) that could be inserted into the heart arteries to expand the narrowed segments. Since then, over 300,000 heart angioplasties were being performed annually by the mid 1980s. As the wall of the artery is elastic, there is a natural tendency for the wall of the narrowed segment to spring back or elastically recoil once the expanded balloon was deflated. Meanwhile, if the balloon had been expanded excessively in a hardened narrowed segment, there is also a risk of causing a significant tear in the arterial wall. To overcome these problems, thin cylindrical metal meshes (stents) that are wrapped onto the balloon catheters were used. The first balloon-expandable heart artery stent, called the Palmaz-Schatz stent, was made available in 1989.
Nevertheless, the expansion of the stent might cause trauma to the arterial wall and the healing of the stented segment might sometimes cause formation of scar tissue that will grow through the openings in the mesh and narrow the arterial lumen. The presence of a metallic scaffold within the heart artery also raised the risk of clot formation within the stent during the first year. The incidence of scar tissue growing into the stent and causing narrowing of the heart arteries (in-stent restenosis or ISR) was as high as 30 percent. For diabetics with small arteries, the incidence could even be higher. In order to solve these issues, drug-eluting stents (DES) were then developed. The metallic stents were enclosed within a very thin layer of polymer onto which drugs were coated. These drugs are released gradually over a period of time to reduce the likelihood of scar tissue formation. In 2002, the first commercially available DES, Cypher stent, was launched. The use of DES can cut ISR to a few percent. By 2004, DES was used in the large majority of heart artery angioplasties. DES can undoubtedly reduce incidence of restenosis significantly, but the problem of clot formation within the stent remains. This lead to development of an entirely new stent made of polymers that will be resorbed by the body over time without the need for long-term blood thinning therapy. Using a stent that completely dissolves in the body not only reduces the risk of bleeding complications but also results in substantial cost savings. The absence of a permanent metallic scaffold in heart arteries and the restoration of natural vessel function benefit the young and active because the heart artery can respond appropriately to demands of exercise. Moreover, it is also possible to visualize the stented heart artery with non-invasive imaging methods such as magnetic resonance imaging, which does not require any injection of contrast and has no X-ray radiation. In 2012, Abbott launched Absorb Bioresorbable Vascular Scaffold (BVS), a polymer stent that has a radial strength comparable to metallic stents. It is capable of opening a blocked heart artery like a metallic stent but is mostly dissolved into the body after 2 years. The artery can eventually return to its normal state and resume its normal functions and is not constrained in its movement by a permanent metallic scaffold. While the new invisible stents will not replace DES completely yet due to high cost, their better design will make them increasingly used in a large majority of angioplasty procedures when they become more affordable later on with the availability of more competitors.
|
||||||||||||||||||||||||
 |
 |
|||||||||||||||||||||||
Copyright
2007-2012 © HowToPreventHeartDisease.com . All Rights Reserved.d........ |
||||||||||||||||||||||||
