Advances in Treating Coronary Artery Disease
The human heart—a fist-sized muscle that pumps 75 gallons of blood every hour of every day through the 12,400 miles of arteries and veins that make up the human circulatory system. All this hard work takes its toll, though, as illustrated by the fact that in the United States alone more than 60 million people have some form of cardiovascular disease. The most common form of heart disease is ]]>coronary artery disease]]> , which is caused by ]]>atherosclerosis]]> —a "hardening" or thickening of the arteries that feed the heart.
Atherosclerosis is caused by gradual damage to the interior wall of an artery. The damage leads to the development of a thickening and roughening of the wall's surface called plaque. Although atherosclerosis is a relatively slow process, over time the plaque builds up to a point where the artery becomes so narrowed that blood flow is severely impaired.
Like any other muscle in the body, the heart needs a constant supply of blood to nourish it with oxygen and nutrients. It receives its blood supply via a "crown" of coronary arteries. When one (or more) of these arteries becomes partially or totally blocked, the heart begins to suffer the effects of decreased blood flow. If left untreated, symptoms ranging from ]]>angina]]> (chest pain) to a ]]>myocardial infarction]]> (heart attack) can occur. In most cases, the cause of the blockage is atherosclerosis.
Standard Treatments and New Twists
When discovered in its early stages, atherosclerosis can be controlled through lifestyle changes and medications. In many cases, however, such as when one or more coronary arteries is more than 70% blocked, more direct procedures are needed to clear the blockage. And, of these procedures, the most common is a nonsurgical procedure known as balloon ]]>angioplasty]]> .
After reviewing a very sophisticated series of x-rays and tests called an ]]>angiogram]]> that pinpoint the location of the blockages, a cardiologist may recommend an angioplasty procedure.
Generally performed in a hospital's ]]>catheterization]]> lab, rather than an operating room, a specialist in this particular procedure inserts a thin, flexible catheter with a deflated balloon at its tip into the arm or leg. The catheter is threaded through the artery until it reaches and passes through the blockage. At this point, the balloon is slowly inflated, which flattens the plaque against the artery wall. This widens the artery opening and allows blood to again flow at a normal (or near normal) rate.
If other coronary arteries are blocked, the catheter is moved and the procedure is repeated.
Angioplasty Plus Stents
Millions of angioplasties have been successfully performed since the procedure was first developed in the 1970s. And a number of improvements have been developed that further enhance its effectiveness.
One of the most successful improvements has been the addition of ]]>stents]]> to the procedure. Now included in approximately 70%-90% of all angioplasties performed, stents are used to prop open an artery once the blockage has been cleared. Following completion of the angioplasty, the stent—made of tiny wire mesh tubing—is collapsed over a balloon-covered wire and maneuvered through the catheter to the spot where the artery has been cleared. The balloon is then inflated, expanding and locking the stent into place, where it remains permanently to help keep the artery open.
Unfortunately, reclosure of the artery (restenosis) occurs in as many as one-third of patients and often requires a repeat angioplasty. The use of drug-coated stents, which are covered with a medication that slows the scarring process within the stent, is relatively new, but appears to substantially reduce the rate of restenosis. (And, in case you're wondering, stents—though made of metal mesh—don't set off airport metal detectors!)
The Pros and Cons of Angioplasty
Although widely used and highly successful (the initial success rate is about 90%), angioplasty is a procedure that does involve some risk. It's also important to note that despite its high degree of success in treating atherosclerosis, angioplasty is not a cure.
A recent study called the COURAGE trial showed that angioplasty with stenting did not reduce the risk of death from heart disease or the incidence of ]]>heart attacks]]> for patients with stable angina (cardiac pain) any more then aggressive medical therapy alone, although the procedure was more effective in controlling pain. Therefore, after the angioplasty, a strict regimen of diet, exercise, and medication must be followed to keep the disease in check—especially considering that an average of 50% of patients will later require a repeat procedure or more intensive, invasive treatment.
Coronary Artery Bypass Graft (CABG)
What if your cardiologist feels that your atherosclerosis is severe enough to warrant the more invasive treatment? The next step may be coronary artery bypass surgery, also known as ]]>coronary artery bypass graft]]> (CABG, or "cabbage").
More than 500,000 CABG procedures are done in the United States every year, and it is diagnosed by the following factors:
- Three or more blocked arteries
- Blockage of the left main coronary artery
- Another medical condition, such as ]]>diabetes]]> , or another factor, such as advancing age, that makes CABG necessary or preferable to angioplasty
CABG is an invasive surgery in which the chest is opened through the breastbone and the heart is stopped. The patient is placed on a heart-lung machine, which keeps the blood oxygenated and flowing during the surgery. A large blood vessel is then taken from the leg, chest, or stomach and attached (grafted) to the heart, thus forming a "detour" artery through which blood can flow. The breastbone is then reattached and the chest is closed.
Because of its invasive nature, CABG entails a greater degree of procedural and postoperative risk than does an angioplasty, as well as increased recovery time. After a five- to six-day hospital stay, patients are sent home with instructions to gradually increase their physical activity at home over the next six weeks. They are also advised not to drive, or to play golf, tennis, or any other activity that puts their arms into extreme motion. After six weeks at home, patients are usually encouraged to return to work and to gradually resume "normal" life, including sexual relations.
Minimally Invasive Direct Coronary Artery Bypass (MIDCAB)
Although relatively new, the minimally invasive direct coronary artery bypass (MIDCAB) has begun to offer patients and their surgeons an alternative to CABG. Like CABG, MIDCAB creates a grafted detour around the heart's blocked arteries. But because it's performed through a small incision in the chest with the help of a tiny video camera—and does not require stopping the heart during surgery—it's a less invasive procedure than the traditional CABG. As a result, MIDCAB may shorten hospital stay and recovery time.
Unfortunately, MIDCAB is not a viable alternative for everyone. While the decision will vary with each individual patient, it is generally recommended only for those who are under age 65, who are in otherwise good health, and who have had an unsuccessful angioplasty (or for whom an angioplasty is not warranted).
Transmyocardial revascularization (TMR) appears to be a good procedure for patients who cannot undergo bypass surgery. TMR uses lasers to "shoot" 20-45 small, pencil lead-sized "channels" in the heart muscle. These channels quickly close up on the outside, but remain open on the inside of the heart, creating, in essence, new vessels for blood to flow through freely. These new channels bypass the blocked arteries and are able to supply the heart with oxygen and nutrients.
TMR has produced promising early results in three large multi-center clinical trials. It has also recently received FDA approval for use in patients with severe angina who have no other treatment options. Studies have shown that the angina of 80%-90% of patients who've had this procedure has significantly improved (at least 50%) one year after surgery. There's still limited follow-up data as to how long the beneficial effects of this procedure might last, however.
Enhanced External Counterpulsation (EECP)
EECP is a noninvasive procedure where patients undergo a series of 35 1-hour sessions over 7 weeks in which air bag-like blood pressure cuffs wrapped around the legs are inflated and deflated in sequence with the heart’s rhythm. How this works is not fully understood, but it has been shown to reduce the frequency of chest pain and the need for nitroglycerine in patients with significant CAD who are not good candidates for angioplasty or CABG.
American Heart Association
National Heart, Lung, and Blood Institute
Heart and Stroke Association of Canada
Canadian Public Health
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Boden W, O'Rourke R, Teo K, et al. Optimal medical therapy with or without PCI for stable coronary disease. New J Med. 2007;356:1503-1516.
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National Heart, Lung, and Blood Institute. Avaialble at: http://www.nhlbi.nih.gov .
Raizner AE, et al. Inhibition of restenosis with beta-emitting radiotherapy: report of the Proliferation Reduction with Vascular Energy Trial (PREVENT). Circulation. 2000;102:951-958.
Last reviewed February 2009 by ]]> Igor Puzanov, MD ]]>
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