Angioplasty - Heart Surgery: Heart Disease

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Angioplasty

In the late 1970s, a new technique revolutionized cardiology. This innovation permitted doctors to open narrowed or blocked coronary arteries with special catheters (long flexible tubes) that had inflatable balloons at their tips. The medical term for this technique is percutaneous transluminal coronary angioplasty (PTCA), but it's better known as angioplasty. The term angioplasty refers to the reshaping of the narrowed segment of a blood vessel in the course of the procedure.

Although the introduction of angioplasty represented a significant advance, and success rates improved over the years, one troubling complication remained: restenosis, a renarrowing of an artery in the same spot that angioplasty had cleared. Restenosis usually happens within three to six months of the original procedure and may occur for several reasons. One cause is elastic recoil: A vessel stretched by angioplasty gradually returns to its original size. A second reason is intimal hyperplasia, which involves a vigorous growth of cells lining the vessel wall. Intimal hyperplasia can occur as part of the healing process following the trauma caused by angioplasty.

In the 1990s, cardiologists began using devices called stents to prop open arteries after angioplasty. A stent looks like a miniature chain-link fence rolled into a tube. By placing a stent inside the treated blood vessel, cardiologists were able to keep arteries from recoiling, thus preventing one serious complication of angioplasty. But the early stents did not stop restenosis.

That problem has now largely been solved, thanks to the introduction of drug-coated stents in 2003. (Although relatively new in the United States, these stents have been in wide use in Europe, South America, and elsewhere for years.) The first of these devices to hit the market was the Cypher stent, which is coated with sirolimus, a substance that cools inflammation and stops muscle cells in the artery wall from growing and dividing. In 2002, major randomized trials compared the old and new stents. The outcomes were clearly much better for people who received sirolimus-coated stents. Only about 1 in 20 people who get angioplasty plus a Cypher stent have enough regrowth in the artery wall to again limit blood flow, compared with 1 in 3 who get a bare-metal stent. Put another way, the drug-coated stent works 95% of the time. In 2004, a major trial with a different type of drug-coated stent — using paclitaxel, a medication used for years to treat cancer — produced results similar to the earlier study of the Cypher stent. There is as yet no evidence proving that one of these drug-coated stents is better than the other. However, there is evidence that drug coated stents cause other problems—namely blood clots in the artery they are propping open.

Still, angioplasty is now the most effective way to treat people with heart attacks. It is also used to treat narrowing at curves in coronary arteries, disease in several vessels, and even narrowing in coronary artery bypass grafts. Because of technical advances in angioplasty, doctors are now willing to perform it on some people for whom it used to be considered too risky. At this point, angioplasty usually includes stent insertion, but there are some exceptions. A stent is not used when blood vessels are too small or when narrowings occur at curves, making insertion too difficult.

Meanwhile the technology keeps advancing. Several manufacturers, for instance, are developing and testing stents that are absorbed into the body a few months after insertion. Although this might seem counterintuitive — after all, the stent is supposed to prop an artery open — some research indicates that benefit is most important in the first few months after surgery. The implications are clear: Angioplasty keeps getting better.

Angioplasty, step by step

A person undergoing angioplasty remains awake during the procedure, but receives local anesthesia. As in routine coronary arteriography (see "Coronary arteriography [angiogram]"), angioplasty starts with the physician inserting a catheter into an artery in an arm or leg and guiding it through the blood vessels to the openings of the coronary arteries. Inside this catheter is an even thinner catheter, which has an inflatable balloon near its tip. And inside that catheter is an even thinner wire with a soft tip that can snake through tight narrowings and punch through clots, but is unlikely to damage the wall of the coronary artery.

The cardiologist guides the wire gently down the artery until the tip is beyond the narrowing. (If the coronary artery is completely blocked, the physician may try to push the wire through the obstruction.) Once the wire has crossed the stenosis (blockage), the catheter with the balloon slides down the wire until the balloon is adjacent to the atherosclerotic plaque (see Figure 8). From outside the body, the physician inflates the balloon, which cracks and compresses the atherosclerotic plaque, stretches the underlying normal arterial wall, and so widens the artery.

Figure 8: Balloon angioplasty To open an artery narrowed by plaque, the cardiac surgeon feeds a catheter to the site of the blockage and threads a thin, flexible guide wire through the narrowing (A). The balloon catheter advances along the guide wire until it's positioned directly inside the narrowed area (B). As the balloon inflates, the plaque stretches and cracks, allowing freer passage of blood through the now-reopened artery (C).

Stent placement is also done with the balloon catheter. The stent is made of a springy, collapsible metal mesh (see Figure 9). During angioplasty, the doctor places the collapsed stent over the balloon catheter. When the balloon is inflated at the site of the blockage, the stent also expands. The doctor withdraws the catheter and leaves the expanded stent in place.

Figure 9: Drug-coated stents One way to prop open a blood vessel is to insert a mesh cage called a stent into the artery. But plaque, in a process called restenosis (A), can gradually clog the stent. To help keep such arteries clear, scientists have developed drug-coated stents (B).

Following a stent procedure, you take medications to prevent blood clots that could lead to restenosis. Aspirin must be taken indefinitely, no matter what type of stent is used. In addition, clopidogrel (Plavix) is prescribed for at least one month if a bare metal (an uncoated stent) is inserted, and it needs to be continued longer if a drug-coated stent is used. How long is still under investigation, but the American Heart Association currently recommends at least one year. Because these medications increase the risk of bleeding, patients getting angioplasty who are also likely to need surgery within a year should receive bare metal stents.

Risks of angioplasty. No medical procedure is risk-free. Angioplasty triggers minor heart attacks in about 4 in 100 people, and just under 1 in 100 die from complications of the procedure. Even with the drug-coated stents, about 5 in 100 people need to repeat the procedure because the reopened artery narrows.

What are the signs of restenosis? There are two main ways to tell if a stent has collapsed or if it is being overgrown with tissue: symptoms such as chest pain, and heart-function tests. If you had a stent inserted several years ago, before the drug-coated stents became available, there is no reason to worry unless you start experiencing chest pain or other symptoms of angina. In that case, call your cardiologist and ask for an evaluation. But if you feel fine, assume that the stented artery remains open.

Are the newer stents safe? They are probably as safe as bare metal stents, and perhaps over time they will be proven to be safer. If used under the right circumstances, they certainly cause less overgrowth of scar tissue. However, they cause a higher risk of blood clots forming in the coronary arteries compared to bare metal stents. And taking a combination of clopidogrel and aspirin to prevent clots results in more episodes of serious bleeding than aspirin alone.

Is angioplasty for everyone? No. Although the advent of drug-coated stents has greatly reduced the problem of restenosis, and more people are likely to undergo coronary angioplasty with stent placement, cardiologists are beginning to recognize that not everyone needs this procedure. Angioplasty is terrific for relieving symptoms caused by an obstruction in a coronary artery, but it doesn't solve the underlying problem, atherosclerosis. Angioplasty may open one or more narrowed arteries, but it is likely that other atherosclerotic plaques lurk elsewhere. For this reason, even after people undergo angioplasty, they still have to take other steps to reduce their risk for heart attack, such as eating better, getting more exercise, and taking medications as prescribed. People who discover they have a partial blockage in an artery during a medical test, but who do not have pain or other symptoms, are probably best advised to forgo angioplasty because it doesn't solve the underlying problem of atherosclerosis and will do nothing to prevent a heart attack.

A large, well-done study presented at the American College of Cardiology meeting held in March 2007 found that even in people with chest pain, angioplasty might not be better than medications. The study found that in people with stable coronary disease—that is, people who have chest pain with exertion but not at rest—angioplasty with stenting was no better than taking medication and lifestyle modifications. In the study, more than 2,000 people with stable coronary disease were treated with medications and counseled on a healthy lifestyle for heart disease. Half of the people also got angioplasty and stenting. At the end of five years, the groups had similar rates of heart attack and death. People in the stenting group reported less chest pain at the three-year mark, but the groups were equal in this regard at the end of five years.

Radiation is another option. Although drug-coated stents have become the first choice for reducing the risk for in-stent restenosis, radiation administered from inside the artery provides another option for some people. After clearing the new growth from inside the stent, the doctor guides a string or ribbon of rice-sized radioactive seeds along the same catheter, positioning it inside the stent and letting it sit for several minutes. Radiation from the seeds inhibits the fast-growing cells that cause restenosis. The FDA has approved several different radiation delivery systems for treating in-stent restenosis.

Last updated:	May 03, 2007