Peripheral Arterial Disease

In peripheral arterial disease (also called peripheral vascular disease), blockages in peripheral arteries reduce or stop blood flow.

Peripheral arteries carry blood to tissues other than those of the brain, heart, and lungs. Most commonly, peripheral arterial disease develops in the legs. Having this disease is a bit like having clogged plumbing.

Peripheral arterial disease is very common among older people. The most common cause is atherosclerosis, which becomes increasingly common as people age. Atherosclerosis usually causes gradual blockage of arteries. Peripheral arterial disease may also result from sudden, complete blockage by part of a blood clot that formed in the heart, aorta, or another artery. Part of the clot can break off and travel through the bloodstream (becoming an embolus) until it reaches an artery that is too small for it to pass through. Some disorders (such as atrial fibrillation, aneurysms, and clotting disorders) increase the risk of blood clots.

Peripheral arterial disease damages tissues by depriving them of blood and thus oxygen and nutrients. The damaged tissues may die if blood flow is not improved.

Peripheral arterial disease usually causes problems in the legs first. Problems may be first noticed during walking because muscles need more oxygen during physical activity. As the disease progresses, it may affect more peripheral arteries. Sometimes arteries that carry blood to internal organs such as the stomach or intestines are affected. If peripheral arterial disease is caused by atherosclerosis, the arteries that carry blood to the heart, brain, or lungs may also be affected. Then, the risk of heart attacks, heart failure, and strokes is increased.

Peripheral arterial disease can be prevented in many people. Treatment can help control symptoms and make problems less likely to develop.

Symptoms

At first, peripheral arterial disease usually causes no symptoms. When symptoms occur, they usually involve the legs.

Most commonly, pain, tightness, or weakness is felt in the legs or buttocks during walking. This symptom is called intermittent claudication. Claudication results from a gradual blockage of leg arteries. Often, both legs are affected, but one leg can be affected more than the other. The pain, usually felt in the calves, is typically dull and achy. The legs may feel as if they are being squeezed. The pain often begins predictably. For example, it may develop after a person walks a certain number of blocks. Resting for a few minutes relieves the pain. If the blockage enlarges, the pain may begin after less activity or last longer.

At first, the leg may look almost normal. But as the blockage enlarges, muscles may shrink (atrophy). The skin may become shiny, thin, and cracked. Sores may develop on the toes or foot. Sores and wounds, including scratches and cuts, tend to heal slowly and incompletely and can easily become infected. Redness, warmth, pain, or pus around a sore or wound or a fever may indicate an infection.

If an artery is almost completely blocked, pain may occur even when a person is resting. The pain may feel like pins and needles or severe burning. It is often worse at night. The foot may become cool, pale, or turn blue. Toes or parts of the foot may die, becoming black and numb (a condition called dry gangrene). Dry gangrene sometimes leads to an infection called wet gangrene. The infection can spread up the leg within hours, destroying large amounts of tissue. The infection can also spread within the bloodstream. In either case, the person can become gravely ill very quickly, sometimes within a few hours. When the infection spreads, fever and low blood pressure usually develop, and some people die.

Excruciating pain can occur suddenly when an artery is blocked by an embolus. The pain can become unbearable within seconds. The affected foot or leg may become cool, pale, or blue within seconds and numb within minutes or hours.

Other symptoms may occur, depending on which arteries are blocked, which organ is deprived of blood, and how quickly the blockage developed. For example, gradual blockage of arteries to the intestines may cause abdominal pain that is worse after eating (bowel ischemia). Sudden blockage of arteries to the stomach or intestines can cause sudden, severe abdominal pain. In men, blood flow to the penis may be reduced, causing erectile dysfunction.

Diagnosis

To assess the blood supply to the legs, a doctor usually checks the pulse in the feet and legs. If arteries are extensively blocked, the pulse is decreased or absent. Using a blood pressure cuff, the doctor may measure blood pressure in the arms and legs. Normally, blood pressure in the thighs is as high as or a bit higher than that in the arms. If arteries in the legs are blocked, blood pressure in the part of the legs above the blockages is likely to be much higher than blood pressure in the arms. But blood pressure below the blockages is usually much lower than that in the arms. Several blood pressure cuffs may be used to check for differences in blood pressure in various parts of the leg. Blood pressure is measured on both sides of the body. Normally, the pressures are about equal. But blood pressure may be much lower on one side if arteries are blocked.

Doppler ultrasonography can be used to measure blood flow and thus can help determine the extent of the blockage. This test is simple and painless. It uses sound waves rather than radiation to produce an image. Slight blockage may not be detected if the test is done when the person is resting. So sometimes the test is done while the person is exercising the leg.

Angiography done with a long, thin tube (catheter) is the most accurate test for determining the location and extent of a blockage. In this test, dye is injected through the catheter inserted in an artery and positioned as close as possible to the affected area. Then x-rays are taken. Magnetic resonance angiography (MRA) is almost as accurate as angiography with a catheter but is safer and more comfortable. No radiation is involved. A contrast agent may be injected, but a needle (not a catheter) is used, and the needle is inserted into a vein (not an artery) and is removed as soon as the injection is complete.

Once a blockage is detected, other tests may help determine the cause. Blood tests are usually done to look for disorders that can cause atherosclerosis or blood clots. Tests are also done to determine whether atherosclerosis has affected arteries that carry blood to the heart or brain. Tests to check for coronary artery disease, such as electrocardiography or exercise echocardiography (ultrasonography of the heart during exercise stress testing), are commonly done, especially if surgery is planned. Ultrasonography may be used to check the arteries in the neck, because they carry blood to the brain.

Treatment

The goals of treatment include preventing blockages from worsening and relieving symptoms (usually claudication). Treatment may also improve the condition of the skin and help sores and wounds heal. Treatment may even prevent death due to a heart attack or stroke.

Treatment differs depending on whether the blockage occurred suddenly or developed gradually. A sudden blockage requires emergency treatment. The goal is to open the artery as quickly as possible so that tissues receive oxygen and do not die. The effects of sudden blockage may be reversed if treatment is given within hours. To open the artery, doctors try to dissolve or remove the blockage. If a blood clot is causing the blockage, a drug that dissolves clots (thrombolytic drug), such as tissue plasminogen activator or streptokinase, may be given. Sometimes these drugs can be applied directly to the clot through a catheter during angiography. If drugs do not work, surgery may be needed to remove the clot. If the clot is in a large artery, surgery may be the treatment of choice.

For blockages that developed gradually, treatment usually involves correcting or treating the risk factors for atherosclerosis. These measures may prevent atherosclerosis from worsening and may even make some of the blockages in arteries shrink.

Gradually exercising the legs more can help relieve symptoms. For example, a person should walk until symptoms occur, stop and rest until symptoms resolve, then walk further. This strategy, done repeatedly, gradually increases the distance the person can walk.

Drugs that prevent platelets from sticking together (anti-platelet drugs), such as aspirin, ticlopidine, and clopidogrel, may be prescribed. Platelets are small cell-like particles in the blood. They stick together to help blood clot and plug breaks in blood vessels. Thus, antiplatelet drugs can prevent clots from forming and causing more blockages. These drugs relieve symptoms. They may also prolong life because they help prevent heart attacks and strokes.

Drugs such as cilostazol and pentoxifylline, taken by mouth, are used to treat claudication, but the effectiveness of pentoxifylline has not been proved. Acetyl-L carnitine, ginkgo biloba, and vitamin E supplements are used less often. Their effectiveness is uncertain. Many other treatments, including drugs that may stimulate the growth of new blood vessels, are being studied.

Somewhat like a plumber trying to clear a clogged drain, doctors may try to mechanically open blocked arteries. For example, if an artery is blocked in only one place, a catheter with a small balloon can be inserted through the skin and into the blocked artery. Once in place, the balloon is inflated and used to clear the blockage. This procedure is called percutaneous transluminal angioplasty (PTA). It can often be done at the same time as angiography. During angioplasty, a small tube of wire mesh (stent) can be inserted into the artery to keep it open.

If gradual blockage causes severe symptoms, such as pain during rest, surgery to open the blocked arteries may be necessary. Many types of surgery can be effective. For example, if the blockage is caused by atherosclerosis, the blocked portion of the artery can often be replaced with an artificial tube (graft) that bypasses the blockage.

Good foot care helps prevent infection or gangrene. Each day, the feet, legs, and sores (if present) should be washed with a gentle soap. Sores should be covered with clean, dry bandages. Keeping the legs below the level of the heart helps improve blood flow and thus may speed healing. Tight shoes should not be worn. A doctor should check any sore on the foot that has not begun to heal after several days. If the sore is infected, doctors usually prescribe antibiotics. People with an infected sore may need to be hospitalized.

If people have persistent pain, severe infection, or gangrene, the leg may have to be surgically removed (amputated). A leg may be amputated below the knee, above the knee, or at the hip. Sometimes only a toe or part of the foot is amputated. Doctors usually recommend an artificial leg (prosthesis). Taking care of the remaining part of the leg (stump) is crucial. It should be kept clean and dry and checked daily for irritation, redness, and sores. Rehabilitation after amputation is intensive. After surgery, physical therapy is started as soon as the person is able.

Outlook

In many people with claudication, blockage of leg arteries continues to progress. However, symptoms often do not worsen as much as blockage does because the body can form new vessels to aid blood flow. Formation of new blood vessels is called collateral circulation.

See the figure Collateral Circulation: A Way Around a Blockage.

If peripheral arterial disease is part of widespread atherosclerosis, blood flow to a vital organ such as the heart or brain may be blocked. Then, serious consequences such as a heart attack or stroke may occur. Death may occur within months or years. It is often due to a heart attack or stroke.