|The Merck Manual of Medical Information--Home Edition
|Section 3. Heart and Blood Vessel Disorders
Peripheral Arterial Disease
Occlusive arterial disease includes both coronary artery disease, which can lead to a heart attack, (see page 126 in Chapter 27, Coronary Artery Disease) and peripheral arterial disease, which may affect the abdominal aorta and its major branches as well as the arteries of the legs. Other peripheral arterial diseases are Buerger's disease, Raynaud's disease, and acrocyanosis.
Most people with peripheral arterial disease have atherosclerosis, a disease process in which fatty material accumulates under the lining of the arterial wall, gradually narrowing the artery. (see page 118 in Chapter 26, Atherosclerosis) However, a partial or complete occlusion of an artery can result from other causes, such as a blood clot. When an artery narrows, the parts of the body it serves may not receive enough blood. The resulting decrease in oxygen supply (ischemia) can come on suddenly (acute ischemia) or gradually (chronic ischemia).
To help prevent peripheral arterial disease, a person should reduce the number of risk factors for atherosclerosis, such as smoking, obesity, high blood pressure, and high cholesterol levels. (see page 120 in Chapter 26, Atherosclerosis) Diabetes also is a major cause of peripheral arterial disease, and appropriate treatment of diabetes may delay the arterial disease. Once peripheral arterial disease appears, treatment is directed at its complications--severe leg cramps while walking, angina, abnormal heart rhythms, heart failure, heart attack, stroke, and kidney failure.
Abdominal Aorta and Branches
Obstruction of the abdominal aorta and its major branches may be sudden or gradual. A sudden, complete obstruction usually results when a clot carried by the bloodstream lodges in an artery (embolism), a clot forms (thrombosis) in a narrowed artery, or the artery wall tears (aortic dissection). An obstruction that develops gradually usually results from atherosclerosis; less often, it results from an abnormal growth of muscle in the artery wall or pressure from an expanding mass, such as a tumor, outside the artery.
A sudden, complete obstruction of the superior mesenteric artery, a major branch of the abdominal aorta that supplies a large part of the intestine, is an emergency. A person with such an obstruction becomes seriously ill and has severe abdominal pain. Initially, vomiting and urgent bowel movements usually occur. Although the abdomen may feel tender when a doctor presses on it, the severe abdominal pain is usually worse than the tenderness, which is widespread and vague. The abdomen may be slightly distended. Through a stethoscope, a doctor initially hears fewer bowel sounds than normal in the abdomen. Later, no bowel sounds can be heard. Blood appears in the stool, though at first it can be detected only by laboratory tests. Soon the stool looks bloody. Blood pressure falls, and the person goes into shock as the intestine becomes gangrenous.
A gradual narrowing of the superior mesenteric artery typically causes pain 30 to 60 minutes after eating because digestion requires an increased blood flow to the intestine. The pain is steady, severe, and usually centered on the navel. This pain makes people afraid to eat, and they may lose considerable weight. Because of the reduced blood supply, nutrients may be poorly absorbed into the bloodstream, contributing to the weight loss.
When a clot lodges in one of the renal arteries, the branches that supply the kidneys, a sudden pain occurs in the side, and the urine becomes bloody. Gradual obstruction of the arteries to one or both kidneys usually results from atherosclerosis and may lead to high blood pressure (renovascular hypertension), which accounts for 5 percent of all high blood pressure.
When the lower aorta is abruptly obstructed where it divides into two branches that pass through the pelvis to deliver blood to the legs (iliac arteries), both legs suddenly become painful, pale, and cold. No pulse can be felt in the legs, which may become numb.
When gradual narrowing occurs in the lower aorta or one of the iliac arteries, the person feels muscle tiredness or pain in the buttocks, hips, and calves while walking. In men, impotence is common with narrowing of the lower aorta or both iliac arteries. If the narrowing occurs in the artery that begins at the groin and goes down the leg to the knee (femoral artery), a person typically feels pain in the calves while walking and has weak or no pulses below the obstruction.
Whether a person survives a sudden obstruction of the superior mesenteric artery and whether the intestine can be saved depend on how fast the blood supply is restored. To save precious time, a doctor may send a patient for emergency surgery without even taking x-rays. If the superior mesenteric artery is blocked as the doctor suspects, only immediate surgery can restore the blood supply fast enough to save the person's life.
With a gradual obstruction of blood flow to the intestine, nitroglycerin may relieve the abdominal pain, but only surgery can relieve the obstruction. Doctors use Doppler ultrasound and angiography (see pages 76 and 78 in Chapter 15, Diagnosis of Heart Disease) to determine how extensive the obstruction is and whether to operate.
Blood clots in the hepatic and splenic arteries, the branches supplying the liver and spleen, generally aren't as dangerous as obstructed blood flow to the intestine. Even though an obstruction can cause injury to parts of the liver or spleen, surgery is rarely needed to correct the problem.
Early surgical removal of a clot from a renal artery may restore kidney function. With a gradual obstruction of a renal artery, doctors can sometimes use angioplasty (a procedure in which a balloon is inserted into the artery and inflated to clear the obstruction), but usually they must remove or bypass the blockage surgically.
Emergency surgery can clear a sudden obstruction of the lower aorta where it divides into two branches to deliver blood to the legs. Sometimes doctors can dissolve the clot by injecting a thrombolytic drug, such as urokinase, but surgery is more likely to be successful.
Arteries of the Legs and Arms
With a gradually narrowing leg artery, the first symptom is a painful, aching, cramping, or tired feeling in leg muscles during physical activity; this feeling is called intermittent claudication. Muscles hurt when the person walks, and the pain comes on faster and is more severe when the person walks quickly or uphill. Most commonly, the pain is in the calf, but it can also be in the foot, thigh, hip, or buttocks, depending on the location of the narrowing. The pain can be relieved by resting. Usually, after 1 to 5 minutes of sitting or standing, the person can walk the same distance already covered before feeling pain again. The same kind of pain on exertion is also caused by narrowing of the arteries in the arms.
As the disease gets worse, the distance the person can walk without pain gets shorter. Eventually, the muscles may ache even at rest. The pain usually begins in the lower leg or foot, is severe and unrelenting, and gets worse when the leg is elevated. The pain often prevents sleep. For relief, a person may hang the feet over the side of the bed or rest sitting up with the legs hanging down.
A foot with a severely reduced blood supply is usually cold and numb. The skin may be dry and scaly, and the nails and hair may not grow well. As the obstruction worsens, a person may develop sores, typically on the toes or heel and occasionally on the lower leg, especially after an injury. The leg may shrink. A severe obstruction may cause tissue death (gangrene).
With a sudden, complete obstruction of a leg or arm artery, a person feels severe pain, coldness, and numbness. The person's leg or arm is either pale or bluish (cyanotic). No pulse can be felt below the obstruction.
A doctor suspects an obstruction based on the symptoms the patient describes and a pulse that's diminished or absent below a certain point in the leg. Doctors estimate blood flow to a person's legs in several ways, including comparing blood pressure at the ankle with blood pressure in the arm. Normally, the ankle pressure is at least 90 percent of the arm pressure, but with severe narrowing it may be less than 50 percent.
The diagnosis may be confirmed by certain tests. With Doppler ultrasound, a probe is placed on the person's skin over the obstruction, and the sound of the blood flow indicates the degree of obstruction. (see page 76 in Chapter 15, Diagnosis of Heart Disease) A more sophisticated ultrasound technique, color Doppler produces a picture of the artery that shows different flow rates in different colors. Because it doesn't require an injection, it's used instead of angiography whenever possible.
In angiography, a solution that's opaque to x-rays is injected into the artery. Then x-rays are taken to show the rate of blood flow, the diameter of the artery, and any obstruction. (see page 78 in Chapter 15, Diagnosis of Heart Disease) Angiography may be followed by angioplasty to open up the artery.
People with intermittent claudication should walk at least 30 minutes a day, if possible. When they feel pain, they should stop until it subsides and then walk again. By doing this, they can usually increase the distance they can walk comfortably, probably because the exercise improves muscle function and makes other blood vessels supplying the muscles grow larger. People with obstructions shouldn't use tobacco in any form. Elevating the head of the bed with 4- to 6-inch blocks may help by increasing blood flow to the legs.
Doctors may prescribe a drug such as pentoxifylline in an effort to improve oxygen delivery to the muscles. Other drugs, such as calcium antagonists or aspirin, also may be helpful. Beta-blockers, which help people with coronary artery obstructions by slowing the heart and reducing its need for oxygen, sometimes worsen symptoms in people with leg artery obstructions.
Performing Foot Care
A person with poor circulation to the feet should use these self-care measures and precautions:
- Inspect feet daily for cracks, sores, corns, and calluses.
- Wash feet daily in lukewarm water with mild soap and dry them gently and thoroughly.
- Use a lubricant, such as lanolin, for dry skin.
- Use unmedicated powder to keep the feet dry.
- Cut toenails straight across and not too short. (A podiatrist may have to cut the nails.)
- Have a podiatrist treat corns or calluses.
- Don't use adhesive or harsh chemicals.
- Change socks or stockings daily and shoes often.
- Don't wear tight garters or stockings with tight elastic tops.
- Wear loose wool socks to keep the feet warm.
- Don't use hot water bottles or heating pads.
- Wear shoes that fit well and have wide toe spaces.
- Ask the podiatrist about a prescription for special shoes if the foot is deformed.
- Don't wear open shoes or walk barefoot.
The goal of foot care is to protect circulation to the foot and prevent complications of poor circulation. A person with foot ulcers requires meticulous care to prevent further deterioration that would make amputation of the foot necessary. The ulcer must be kept clean: It should be washed daily with mild soap or salt solution and covered with clean, dry dressings. A person with a foot ulcer may need complete bed rest with the head of the bed raised. A person who has diabetes also must control blood sugar levels as well as possible. As a rule, anyone with poor circulation to the feet or with diabetes should have a doctor check any foot ulcer that isn't healing after about 7 days. Many times, a doctor prescribes an antibiotic ointment. If the ulcer becomes infected, the doctor generally prescribes antibiotics to be taken by mouth. Healing may take weeks or even months.
Doctors often perform angioplasty immediately after they perform angiography. Angioplasty consists of inserting a catheter with a balloon on its tip into the narrowed part of the artery and then inflating the balloon to clear the obstruction. (see illustration, page 126) Angioplasty may require only 1 or 2 days in the hospital and may help the person avoid a major operation. The procedure isn't painful but may be somewhat uncomfortable because the person has to lie still on a hard x-ray table. A mild sedative, but not general anesthesia, is given. Afterward, the patient may be given heparin to prevent blood clots from forming in the treated area. Many doctors prefer giving patients a platelet inhibitor such as aspirin to prevent clotting. A doctor can use ultrasound to check on the outcome of the procedure and make sure that the narrowing doesn't recur.
Angioplasty can't be performed if the narrowing is widespread, if it extends for a long distance, or if the artery is severely and extensively hardened. Surgery may be needed if a blood clot forms over the narrowed area, a piece of the clot breaks off and blocks a more distant artery, blood seeps into the lining of the artery causing it to bulge and close off blood flow, or the person has bleeding (usually from heparin given to prevent clotting).
Besides balloons, devices--including lasers, mechanical cutters, ultrasonic catheters, stents, and rotational sanders--are used to relieve obstructions. No one device has proved superior.
Surgery very often relieves symptoms, heals ulcers, and prevents amputation. A vascular surgeon can sometimes remove a clot if only a small area is blocked. Alternatively, a surgeon may put in a bypass graft, in which a tube made of a synthetic material or a vein from another part of the body is joined to the obstructed artery above and below the obstruction. Another approach is to remove the blocked or narrowed section and insert a graft in its place. Cutting the nerves near the obstruction (an operation called a sympathectomy) prevents the arteries from having spasms and can be very helpful in some cases.
When amputation is needed to cut out infected tissue, relieve unrelenting pain, or stop worsening gangrene, surgeons remove as little of the leg as possible, particularly if the person plans to wear an artificial limb.
Buerger's disease (thromboangiitis obliterans) is the obstruction of small and medium-sized arteries and veins by inflammation triggered by smoking.
Men ages 20 to 40 who smoke cigarettes get Buerger's disease more than anyone else. Only about 5 percent of people with the disease are women. Although no one knows what causes Buerger's disease, only smokers get it, and continuing to smoke makes it worse. Because only a small number of smokers get Buerger's disease, some people must be more susceptible than others. Why and how cigarette smoke causes the problem aren't known.
Symptoms of reduced blood supply to the arms or legs develop gradually, starting at the fingertips or toes and progressing up the arms or legs, eventually causing gangrene. About 40 percent of people with this disease also have episodes of inflammation in the veins, particularly the superficial veins, and the arteries of the feet or legs. People may feel coldness, numbness, tingling, or burning before their doctor sees any signs. They often have Raynaud's phenomenon (see page 136 in this chapter) and get muscle cramps, usually in the arches of their feet or in their legs but rarely in their hands, arms, or thighs. With more severe obstruction, the pain is worse and lasts longer. Early in the disease, ulcers, gangrene, or both may appear. The hand or foot feels cold, sweats a lot, and turns bluish, probably because the nerves are reacting to severe, persistent pain.
In more than 50 percent of people with Buerger's disease, the pulse is weak or absent in one or more arteries of the feet or wrists. Often, the affected hands, feet, fingers, or toes become pale when raised above the heart and red when lowered. People may develop skin ulcers and gangrene, usually of one or more fingers or toes.
Ultrasound tests reveal a severe decrease in blood pressure and blood flow in the affected feet, toes, hands, and fingers. Angiograms (x-rays of the arteries) show obstructed arteries and other circulation abnormalities, especially in the hands and feet.
A person with this disease must stop smoking, or it will relentlessly worsen, and ultimately an amputation may be necessary. Also, the person should avoid exposure to the cold; injuries from heat, cold, or substances such as iodine or acids used to treat corns and calluses; injuries from poorly fitting shoes or minor surgery (such as trimming calluses); fungal infections; and drugs that can narrow blood vessels.
Walking 15 to 30 minutes twice a day is recommended, except for people with gangrene, sores, or pain at rest; they may need bed rest. People should protect their feet with bandages that have heel pads or with foam-rubber booties. The head of the bed can be raised on 6- to 8-inch blocks so gravity helps blood flow through the arteries. Doctors may prescribe pentoxifylline, calcium antagonists, or platelet inhibitors such as aspirin, especially when the obstruction results from spasm.
For people who quit smoking but still have arterial occlusion, surgeons may improve blood flow by cutting certain nearby nerves to prevent spasm. They seldom perform bypass grafts, because the arteries affected by this disease are too small.
Functional Peripheral Arterial Disorders
Most of these disorders result from a spasm of arteries in the arms or legs. They may be caused by a fault in the blood vessels or by disturbances in the nerves that control the widening and narrowing of arteries (sympathetic nervous system). Such nerve defects may themselves be a consequence of blockage from atherosclerosis.
Raynaud's Disease and Raynaud's Phenomenon
Raynaud's disease and Raynaud's phenomenon are conditions in which small arteries (arterioles), usually in the fingers and toes, go into spasm, causing the skin to become pale or a patchy red to blue.
Doctors use the term Raynaud's disease when no underlying cause is apparent and the term Raynaud's phenomenon when a cause is known. Sometimes, the underlying cause can't be diagnosed at first, but usually it becomes apparent within 2 years.
Between 60 and 90 percent of the cases of Raynaud's disease occur in young women.
Possible causes include scleroderma, rheumatoid arthritis, atherosclerosis, nerve disorders, decreased thyroid activity, injury, and reactions to certain drugs, such as ergot and methysergide. Some people with Raynaud's phenomenon also have migraine headaches, variant angina, and high blood pressure in their lungs (pulmonary hypertension). These associations suggest that the cause of the arterial spasms may be the same in all these disorders. Anything that stimulates the sympathetic nervous system, such as emotion or exposure to cold, can cause arterial spasms.
Symptoms and Diagnosis
Spasm of small arteries in the fingers and toes comes on quickly, most often triggered by exposure to cold. It may last minutes or hours. The fingers and toes turn white, usually in a spotty fashion. Only one finger or toe or parts of one or more may be affected, turning a patchy red and white. As the episode ends, the affected areas may be pinker than usual or bluish. The fingers or toes usually don't hurt, but numbness, tingling, a pins-and-needles sensation, and a burning sensation are common. Rewarming the hands or feet restores normal color and sensation. However, when people have long-standing Raynaud's phenomenon (especially those with scleroderma), the skin of the fingers or toes may change permanently--appearing smooth, shiny, and tight. Small painful sores may appear on the tips of the fingers or toes.
To distinguish between arterial blockage and arterial spasm, doctors perform laboratory tests before and after someone is exposed to cold.
People can control mild Raynaud's disease by protecting their trunk, arms, and legs from cold and by taking mild sedatives. They must stop smoking because nicotine constricts blood vessels. For a few people, relaxation techniques, such as biofeedback, may reduce the spasms. Raynaud's disease is commonly treated with prazosin or nifedipine. Phenoxybenzamine, methyldopa, or pentoxifylline occasionally helps. When people have progressive disability and other treatment doesn't work, sympathetic nerves may be cut to relieve the symptoms, but the relief may last only 1 to 2 years. This operation, called a sympathectomy, generally is more effective for people with Raynaud's disease than for those with Raynaud's phenomenon.
Doctors treat Raynaud's phenomenon by treating the underlying disorder. Phenoxybenzamine may help. Drugs that may constrict blood vessels (such as beta-blockers, clonidine, and ergot preparations) may make Raynaud's phenomenon worse.
Acrocyanosis is a persistent, painless blueness of both hands and, less commonly, the feet, caused by unexplained spasm of the small blood vessels of the skin.
The disorder usually occurs in women, not necessarily those with occlusive arterial disease. The fingers or toes and hands or feet are constantly cold and bluish and sweat profusely; they may swell. Cold temperatures usually intensify the blue coloring, and warming reduces it. The condition isn't painful and doesn't damage the skin.
Doctors diagnose the disorder based on persistent symptoms limited to the person's hands and feet along with normal pulses. Treatment is usually unnecessary. Doctors may prescribe drugs that dilate the arteries, but they usually don't help. Very rarely, sympathetic nerves are cut to relieve symptoms.