Coronary Artery Blockage, Angioplasty, Stents and Restenosis: What Happened to Vice President Dick Cheney?
Coronary Artery Blockage and Heart Attacks
Most heart attacks are caused by the rupturing of blockages in coronary arteries. These blockages are made up of unstable plaque, which is a fatty material that collects much like debris in a drainpipe. Physicians hypothesize that fatty deposits collect at points in the arteries that are not continuously smooth, damaged due to an inflammatory process or, simply imperfect since few arteries are perfect. The heart arteries running along the surface are positioned to supply the heart muscle with oxygenated blood, which fuels the heart muscle. The heart requires several arteries to supply ample oxygenated blood to key areas. When plaque ruptures, frequently one of the coronary arteries is blocked, restricting or stopping blood flow. Within a short period, an area of muscle begins to die. A person then begins to experience the symptoms of a heart attack: pain in the chest, shoulder, arms, neck and chin. Up to 30 percent of patients who experience heart attacks do not survive the event.
While physicians are not fully certain of the cause of plaque rupture, the build-up of plaque is related to a number of risk factors including, family history, elevated cholesterol levels, hypertension, cigarette smoking and diabetes.
Angioplasty and Coronary Artery Stents
When a blockage of more than 70 percent is found in coronary arteries, cardiologists will frequently perform an angioplasty where a long catheter (tube) is guided through an incision in the patient's groin or arm and positioned in the artery overlying the heart. At the end of the catheter is a balloon and when properly positioned by the physician is inflated, opening the artery by pressing the plaque against the artery walls. When the artery is sufficiently opened, a small wire mesh cage (stent) is slid over the catheter and positioned in the blockage area. Stents range in size, most are less than a pencil's diameter and less than one inch in length.
Once the stent is successfully placed, the delivery catheter is removed, and the blocked area is held open. A sufficient blood flow is then restored to the heart. Usually, more than one stent is used, and patients may have stents placed in more than one artery.
Restenosis: What Is It and What Can Be Done About It
While the placement of stents can be very effective in preventing future blockage, 20 percent of patients with stents will experience blockage at the sites where stents are placed. This is referred to as restenosis or "in-stent restenosis."
This is the problem most likely experienced by Vice President Dick Cheney where the arteries treated by angioplasty and stents closed. This process of reclosing and why it occurs in some patients and not others is not entirely understood. In part, the length of the blockage and size of artery can predict reclosing. Diabetics are more likely to experience this problem. For this smaller percentage of patients who develop the reclosing within the stent, the problem occurs within six months. Vice President Cheney was quite typical, having experienced symptoms three months following stent placement. The question is, if reclosing occurs, what options remain? (See Figure 1 for an example of the process of initial stent placement to restenosis surgery).
The physicians of the Minneapolis Heart Institute are leaders in the prevention and management of coronary artery restenosis. Currently, we are the only center in the Twin Cities using multiple new and investigational technologies in this regard.
Minneapolis Heart Institute physicians use leading-edge approaches to restenosis
Cardiologists specializing in angioplasty, stents and restenosis are using several methods to care for patients with in-stent restenosis. Techniques used include:
Intracoronary radiation therapy using radioactive isotopes to treat arteries that have reclosed. Following repeat balloon angioplasty, the previous stent area is exposed to radiation to retard growth of cells that cause restenosis.
Stents that deposit drugs to prevent restenosis. In this case, drugs rather than radiation are used for the cell growth problem.
High energy intracoronary ultrasound delivered by specially developed catheters to the treatment zone
We are now investigating these methods to determine which holds the most promise. In a small percentage of people, none of these methods are appropriate. For these patients, we are testing another alternative called angiogenesis, which uses a growth factor to stimulate generation of new blood vessels around the blocked artery. The future of angiogenesis is promising, but developments will take more time and research investments.
We presume that new types of stents and techniques will go a long way to reduce the risk of restenosis and treat the 20 percent of patients with the problem. If restenosis occurs, we are prepared. Currently, Minneapolis Heart Institute physicians perform the highest number of coronary angioplasties and stents in Twin City area hospitals. Our physicians work collaboratively with cardiologists at other regional heart centers who refer restenosis patients for new therapies. This collaboration enhances our collective capabilities and brings leading-edge services and technologies to patients in need.
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