Arteries are the vital channels that carry oxygen-rich blood from the heart to all the body's tissues. When blockages develop, blood flow slows and tissues suffer. That's when heart attacks and strokes occur. But peripheral artery disease (PAD), which gets less attention, is a major problem, too.
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What is Peripheral Artery Disease?
PAD is a form of atherosclerosis, the same disease that causes most strokes and nearly all heart attacks. It most commonly affects the legs, but it can affect arteries anywhere in the body, including the heart and brain. That's why people with PAD have an increased risk of heart attack and stroke and are two to four-times more likely to die from cardiovascular disease than people without PAD.
The disease begins when LDL ("bad") cholesterol passes from the blood into the walls of an artery. Arteries damaged by high blood pressure, diabetes, or smoking are particularly at risk for PAD and cholesterol build-up. As the cholesterol builds up, it triggers inflammation, which adds to the damage.
Unless treatment halts the process, the cholesterol deposit builds up into a plaque or blockage that narrows the artery. Mild narrowing may not produce any symptoms, but moderate narrowing may prevent muscles from getting the extra blood they need during exercise. When blockages are severe, the tissues suffer even during rest. Blood clots can add to the problem.
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Who Gets PAD?
Only about 3% of Americans below age 50 have the problem, but about 20% of people above age 75 have PAD, which is more common in men. In all, about 8 million Americans have PAD.
Because PAD is a form of atherosclerosis, most major heart disease risk factors — smoking, diabetes, abnormal cholesterol levels, high blood pressure and advancing age — also increase the chances of developing PAD. (One exception: ethnicity and chronic kidney disease appear to have a greater influence in PAD than heart disease.) Other risk factors for PAD include:
- Abdominal obesity
- African American heritage
- Chronic kidney disease
- Tendency to form blood clots
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The earliest and most common symptom is called intermittent claudication, which causes cramp-like muscle pain. Claudication occurs when muscles are not getting enough oxygen. The discomfort can occur in the foot, calf, thigh, or buttock, depending on the site of the blockage. Men can also develop erectile dysfunction if PAD strikes in the aorta or iliac arteries because they supply blood to the penis.
PAD can also produce numbness, tingling, weakness or fatigue. Because muscles need more oxygen when they're working, claudication begins during exercise and resolves with a few minutes of rest. People with mild blockages can walk substantial distances before the symptoms set in, but patients with severe PAD may experience distress in just a few yards.
A more serious symptom is rest pain. It occurs when muscles can't get enough oxygen — even at rest — due to severe blockages. It's most common in the foot. At first, the pain is most troublesome when the leg is elevated, particularly in bed at night. But if the disease progresses, the pain can become constant. Even sitting or standing won't relieve it. Patients with moderate to severe PAD can also develop ulcers or other skin problems in their feet and legs. Rest pain usually requires surgery.
The most dangerous symptom is known as critical limb ischemia. Ischemia means tissue damage caused by lack of blood and oxygen. It's triggered by a blood clot that blocks a narrowed artery. Critical limb ischemia requires emergency treatment to prevent amputation, gangrene, or death.
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If you have any of these symptoms, early diagnosis and treatment is critical because lifestyle treatment and medications can be very effective. Many patients with PAD don't have any symptoms but are diagnosed during a doctor's exam or screening test, such as the ankle-brachial index described below. But diagnosis and treatment is important for them, too.
1. Office evaluation
Your doctor will ask about your risk factors for PAD and your symptoms. It's important to rule out other causes of exercise-induced leg pain, especially arthritis of the lower spine (called spinal stenosis).
Your doctor will do a physical exam. This includes checking your blood pressure and the pulses on the top of your feet, at your ankle, behind your knee, and in your groin. It's important for the doctor to check your pulses in both legs and examine your skin. In PAD, the skin may not get enough oxygen-rich blood. Over time, it becomes cool, thin, and shiny, and hair growth is diminished.
Your doctor will also want to check your cholesterol, blood sugar, and kidney function with a blood test.
2. The Ankle-Brachial Index (ABI)
The ABI is a safe, non-invasive test that can detect PAD and estimate its severity. It can be performed in some doctors' offices or in vascular labs. A technician will use a Doppler probe and a blood pressure cuff to measure the systolic blood pressures in your ankles and arms (the brachial artery). To understand how it works, just step on a garden hose. The blockage produced by your foot will reduce water pressure at the nozzle. Similarly, a blockage in a leg artery will lower blood pressure at the ankle.
3. Doppler duplex ultrasound test
This test uses ultrasound to measure blood flow in the legs. It can be done at rest and after exercise. It's a non-invasive, risk-free way to identify the site of a blockage and to determine how narrow the artery is. In general, a narrowing of more than 50% is likely to produce symptoms.
Patients who are candidates for revascularization (see Treatment) procedures require detailed images produced by angiography. Until recently, that meant an invasive test that required puncturing an artery and injecting a dye to allow blockages to show up on x-rays.
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PAD can increase your risk for heart attack and stroke. So people with PAD need to follow a lifestyle that will fight atherosclerosis and keep their arteries healthy. Here are some key elements:
- Avoid tobacco in all forms, including secondhand smoke.
- Eat right. Cut down on saturated fat (from red meat and whole dairy products) and trans fat (from stick margarine, fried foods, snack foods, and some baked goods). Eat lots of whole grains, vegetables, fruits, and fish. Restrict sodium (salt), ideally to 1,500 mg a day or less, by avoiding processed foods, salty snacks, dried or canned soups and sauces. If you choose to drink, limit yourself to two a day. Cut down on portion sizes and calories if you are overweight.
- Exercise. Exercise helps with weight, cholesterol, blood pressure and stress but walking triggers leg pain in patients with PAD. What to do? Walk! If you have advanced PAD or heart problems, your doctor may refer you to a medically supervised exercise program. If you get the okay to walk on your own, plan to set aside 30 minutes at least 3 days a week. Walk at a comfortable pace, but stop at the first hint of pain. When your legs feel better, start again and repeat the cycle until your time is up. Walking helps your leg muscles use oxygen better, so in time you'll find yourself walking more and resting less. Many men find that exercise training can double or even triple their pain-free walking distances. And a 2006 study reported that physical activity lowers the overall death rate in patients with PAD.
- Reduce stress. Establish priorities. Talk out your worries. Try relaxation techniques.
- Take care of your feet. Wash them in lukewarm water at least once a day and apply lanolin cream or ointment afterwards. Avoid extremes of temperatures. Never use a heating pad on your feet. Don't put them in hot or cold water. If your bed is cold, wear socks at night. Never go barefoot. Wear cotton socks and properly fitting shoes. Place lamb's wool between overriding toes. Trim your nails carefully. Inspect your feet daily. If your feet ache at night, raise the head of your bed with 6-to 10- inch blocks.
Because PAD is a form of atherosclerosis, your doctor will set strict goals for reducing your risk factors. In most cases, you'll need medication to reach these goals:
- Your LDL ("bad") cholesterol should below 100 mg/dL, or below 70 mg/dL if you have severe disease. Most patients will benefit from a statin drug to reach their goal. In fact, a new study reported that statin therapy reduces the risk of heart attack and stroke in PAD patients.
- Your blood pressure should ideally be 130/80 or less, similar to people with diabetes, kidney disease, and heart disease. Many drugs can help; an ACE inhibitor may be a good choice, since it can increase walking distance in people with PAD.
In addition to these drugs, nearly every patient with PAD will benefit from an anti-platelet drug to fight blood clots. Many physicians recommend low-dose aspirin (typically 81 to 325 mg daily), with the prescription drug clopidogrel (Plavix) as an alternative.
Two drugs can be prescribed to improve walking distance in PAD. Ask your doctor about the pros and cons of cilostazol (Pletal) and pentoxifylline (Trental, Pentoxil).
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The Bottom Line
PAD may get much less attention than heart attacks and strokes. But it may be the first way you find out that you have too much cholesterol build-up in your arteries. If you are at risk, ask your doctor about PAD at your next check-up.
Harvey B. Simon, M.D. is an Associate Professor of Medicine at Harvard Medical School and a member of the Health Sciences Technology Faculty at Massachusetts Institute of Technology. He is the founding editor of the Harvard Men's Health Watch newsletter and author of six consumer health books, including The Harvard Medical School Guide to Men's Health (Simon and Schuster, 2002) and The No Sweat Exercise Plan, Lose Weight, Get Healthy and Live Longer (McGraw-Hill, 2006). Dr. Simon practices at the Massachusetts General Hospital; he received the London Prize for Excellence in Teaching from Harvard and MIT.