Lower extremity PAD is peripheral arterial disease (PAD) that occurs in the blood vessels of the legs and/or feet. PAD is a form of atherosclerosis – a progressive disease that involves the hardening and narrowing of the arteries due to a gradual buildup of plaque.
Whereas coronary artery disease (CAD) involves the heart’s coronary arteries, PAD occurs outside of the heart. Because it is similar to CAD, PAD is an important risk factor for heart disease. Other forms of PAD include cerebrovascular disease, renal artery stenosis and mesenteric arterial disease.
The primary symptom of lower extremity PAD is intermittent claudication, a type of pain in the leg that occurs during activity, such as walking. The pain is caused by inadequate oxygen supply to the legs, which may occur during physical activity. When physical activity stops, the pain often stops as well. In most cases, the symptoms are mild. In severe cases, however, patients may experience pain while at rest (rest pain) or pain due to tissue loss or gangrene. Advanced cases of PAD can lead to leg amputation as the tissue below the blockage begins to die.
Diagnosis of PAD typically involves a painless measurement called an ankle-brachial index (ABI), in which the blood pressure in the legs is compared to the blood pressure elsewhere in the body. It may also include more complex tests such as duplex imaging, magnetic resonance angiogram (MRA) and/or an angiogram. Treatment often involves medications (e.g., antiplatelet agents), risk factor modification and exercise. More invasive treatments, such as catheter-based procedures and bypass surgery, are also available.
The symptoms of PAD are not inevitable results of the aging process. However, the likelihood of developing PAD does increase with age, which is an uncontrollable risk factor. Other uncontrollable risk factors for this condition include gender, ethnicity and family history.
Risk factors that can be modified include:
Smoking
Lack of regular exercise
Eating a high-fat diet
Obesity
Uncontrolled diabetes or hypertension
High LDL cholesterol
Low HDL cholesterol
Researchers find that controlling these risk factors (particularly smoking) can greatly reduce the risk of PAD.
About lower extremity PAD
Peripheral arterial disease of the lower extremities is atherosclerosis that occurs in the blood vessels of the legs. The primary arteries that supply blood to the legs are the:
Iliac arteries, located inside the lower abdomen
Femoral arteries, located in the thigh
Tibial arteries, located below the knee
Oxygen-rich blood flows down these arteries to supply the muscles of the buttocks, legs and feet. Atherosclerosis impedes the blood flow, much in the same way it can impede blood flow to the heart, by narrowing and hardening the arteries, much in the same way it can impede blood flow to the heart.
The body compensates for the narrowing or blockage of these major arteries to the legs by enlarging smaller arteries to provide the blood flow to the leg. These smaller arteries, which do not have formal anatomical names, are referred to as collaterals. They are essentially alternate routes that the blood takes to reach its destination.
According to the American Heart Association, up to 75 percent of people with PAD have no symptoms and, therefore, may go undiagnosed. However, because atherosclerosis tends to be a widespread condition in the body, PAD can be an important indicator of heart disease and so it is important that the condition is diagnosed as soon as possible. People with PAD have a six to seven times greater risk of cardiovascular problems, such as heart attack, stroke or transient ischemic attack (TIA or mini-stroke), according to the National Institutes of Health (NIH).
Other forms of PAD include cerebrovascular disease, renal artery stenosis and mesenteric arterial disease
Signs and symptoms of lower extremity PAD
The chief symptom of lower extremity PAD is called intermittent claudication. Intermittent claudication is usually caused by a blockage within an artery that interferes with the delivery of oxygen-rich blood to the muscles. Claudication refers to discomfort, pain or weakness in the legs caused by inadequate oxygen supply. Intermittent claudication refers to pain in one or more areas of the legs that comes and goes.
The pain is “intermittent” because it occurs when the muscles require more oxygen during physical activity. The pain most often occurs in the calf, although it can also occur in the foot, thigh or buttock. Intermittent claudication affects the large muscle groups that are below the actual site of blockage.
Intermittent claudication only occurs during periods of physical activity (e.g., running or walking). When the leg muscles are at rest or under minimal stress, the blood and oxygen supply is sufficient to satisfy the muscles and there is no pain. In some patients, the lack of blood and oxygen supply is severe enough to cause constant pain, usually in the foot, and is called rest pain. In this case, even at rest, not enough blood can be delivered to the tissues in the leg. This pain is usually relieved only by hanging the foot down and is painful enough to wake the patient at night. In severe cases, symptoms may also include gangrene, or tissue death, of the extremities.
Other symptoms of PAD of the lower extremities include:
Pale tint to the skin (pallor)
Sores or wounds on the lower extremities that do not heal promptly
Diminished blood pressure in the leg
A weak or absent pulse
Coolness in the extremities
Diagnosis methods for lower extremity PAD
The diagnosis for PAD typically begins with a medical history and physical examination. However, because the condition is highly variable, some studies have found that relying on traditional symptoms to diagnose PAD can result in many missed cases. The characteristic leg pain (intermittent claudication) may appear almost anywhere in the leg, and its intensity varies depending on the severity of the blockage and the duration of the exercise. PAD can also be asymptomatic (without symptoms).
To diagnose PAD, physicians usually rely on a painless, noninvasive test called the ankle-brachial index (ABI). The ABI compares the blood pressure in the leg to the blood pressure in the arm. Normal leg blood pressure should be anywhere from 90 to 110 percent of the blood pressure measured in the arm and abnormalities in this ratio may indicate PAD. By taking the blood pressure at several locations along the length of the leg, the physician can often determine the presence and location of blockage in any leg blood vessels (e.g. iliac, femoral, or tibial).
The ABI involves the use of a Doppler transducer (a small ultrasound device) to hear the blood flow and a blood pressure cuff sphygmomanometer. First, blood pressure in the arm is measured. Then blood pressure of the leg is measured. If the ABI is less than 0.9 (in other words, 90 percent of arm blood pressure) there is usually diminished blood flow to the leg. Values below 0.5 are often associated with severe disease. If the ABI is normal, but the physician still suspects PAD, the patient may be asked to exercise briefly to elevate the blood flow before the test is conducted.
Other tests that may be used to diagnose PAD of the lower extremities include:
Plethysmograms and Doppler studies. These are tests that determine how effective the pulse wave is transmitted to the leg. These tests are painless and non-invasive. They are usually performed in a “vascular laboratory,” which is a facility dedicated to the non-invasive diagnosis of vascular conditions.
At one time, plethysmograms were used frequently in the diagnosis of lower extremity PAD. However, this test has largely been replaced by more advanced imaging tests, such as the Doppler ultrasound. Duplex (or Doppler) imaging is useful in examining specific areas in the leg arteries but does not play the central role in diagnosis that it does for carotid disease artery. It is also painless and noninvasive.
Magnetic resonance angiography (MRA) on the legs. This test uses magnets to produce images of the arteries and veins with similar accuracy to invasive angiograms but without puncturing the artery to inject dye. MRA is also used to identify small arteries in the lower leg that cannot be seen or detected with angiograms or other testing methods. It is usually performed if some form of intervention, such as surgery, angioplasty, stenting or atherectomy, is considered.
Angiogram of the lower extremities. A test in which a dye is injected into the arteries through a small catheter and x-ray images are taken of the vessels. This is still the best way to evaluate the arteries of the legs since it quickly shows all of the arteries and the collateral pathways that have developed.
Treatment options for lower extremity PAD
Treatment begins by controlling the possible underlying causes of the PAD. It is important that patients make any changes they can in order to slow the progression of the atherosclerosis. For example, quitting smoking is seen as the single most important controllable risk factor. For people with diabetes who have PAD, keeping blood pressure under control can be challenging. The American Heart Association recommends a blood pressure lower than 120/80 mmHg (millimeters of mercury) for individuals with diabetes, in order to help reduce the risk of heart attack.
Other risk factors that can be modified include:
Lack of regular exercise
Eating a diet high in fat
Oobesity
Uncontrolled diabetes
Hhypertension
Chronic stress or anger
High LDL cholesterol and low HDL cholesterol.
In many cases, controlling risk factors is enough to treat the disease. Unlike most other forms of PAD, treatment of PAD of the lower extremities is based almost entirely on the relief of symptoms, especially intermittent claudication (pain in the legs while exercising).
However, if the claudication is disabling, or if advanced symptoms are present, the physician may consider a more aggressive treatment. Treatment is typically indicated for patients experiencing any of these symptoms:
Gangrene or tissue loss
Lifestyle-limiting claudication
Non-healing or deteriorating wounds
Rest pain
If intervention is necessary, physicians may use any or all of the following approaches to treat PAD of the lower extremities:
Exercise and medical therapy (medications)
Endovascular (catheter-based) treatments to increase leg blood flow
Surgical treatments to increase leg blood flow
Exercise and medical therapy
Lifestyle changes are the first line of treatment for a patient's intermittent claudication, and the most important lifestyle change is to start a regular and progressive program of exercise. As determined by a physician, the exercise program usually consists of walking once or twice daily to the point of pain, resting until the pain resolves and then walking home. The length of the walk is increased by small increments each week. This type of exercise encourages the body to grow larger collateral blood vessels, which provide an alternate route for blood to flow to leg muscles. If there is significant improvement in symptoms, no further therapy may be necessary.
Historically, there have been few medications available for the treatment of lower extremity peripheral artery disease (PAD). Recently, several studies have shown that cilostazol is an effective agent in diminishing claudication. This drug is now often used in combination with an exercise program in the initial treatment of patients with intermittent claudication. However, cilostazol should not be used by patients with congestive heart failure. Patients with heart disease should discuss the risks of using cilostazol with their physician.
Antiplatelet medications (e.g., aspirin, ticlopidine, clopidogrel), which inhibit the ability of the blood to clot, are very useful before and after procedures aimed at increasing lower extremity blood flow. Studies have found that statins, a class of cholesterol-reducing drugs, can improve pain-free walking time in persons with PAD and claudication.
If the combination of exercise, medical therapy and risk factor management is not enough to effectively treat PAD of the lower extremities, several minimally invasive and surgical procedures are available.
Endovascular procedures
Endovascular procedures rely on catheters to increase blood flow to the legs. The catheter is usually introduced into the artery through the groin, where it is advanced through the vessel until it has reached the narrowed portion. A variety of procedures can be done with different types of catheters, including:
Angioplasty. One of the most common endovascular procedures for the treatment of lower extremity peripheral arterial disease (PAD). This technique uses a balloon-tipped catheter, which is positioned at the site of the blockage. The balloon is then expanded. This breaks the atherosclerotic plaque blocking the artery and pushes the plaque against the artery wall, creating a larger opening in the artery through which blood can flow. This procedure is similar to the one used in blocked coronary arteries in the heart.
Stenting. Stents are sometimes used in conjunction with angioplasty. A stent is an expandable wire-mesh tube that can be deployed from a catheter at the location of the blockage. The stent provides ongoing mechanical support to open the vessel and hold the plaque back. Two recent studies have suggested that stents may have better long-term results that angioplasty alone. Some stents have a drug coating (drug eluting stents) that help prevent an artery from re-narrowing (restenosis) and reduce the risk of blood clots that sometimes form because of the stent. Drug coated stents are not available for lower extremity, only coronary artery disease. All peripheral stents are bare metal. Drug coated stents are under investigation.
Other catheter-based procedures. Sometimes the material blocking the artery is mainly clotted blood (a thrombus). In these cases there is a variety of catheters that can be used. Some use water jets to remove the clot as the catheter is passed through it. This is called thrombectomy. Other catheters are made to deliver drugs that speed the body’s natural ability to dissolve clots. This is called thrombolysis. There are still other catheters that can remove plaque, called atherectomy catheters. Atherectomy catheters are being used more often in recent years. However, currently, there is no evidence that these catheter treatments are superior to angioplasty and stent.
Catheter-based procedures are often the first method of invasive treatment used for patients with lower extremity PAD. They can usually be done on an outpatient basis and require only local anesthetic. Patients can usually return to their normal activity within one to two days.
The downside of catheter-based procedures is relatively high recurrence rates. This is because disease of the lower extremities frequently extends over long segments of the leg arteries, and these long segments often develop new blockages after angioplasty or stenting. For that reason it is important to monitor the treated arteries with ultrasound regularly following the treatment so that any recurrence can be detected early and treated easily before more extensive surgery or other treatments are required.
Surgical procedures
Surgical procedures generally aim to restore blood flow using techniques that directly expose one or more blood vessels (open surgery). Having direct and open control of the blood vessel allows for a number of procedures to be performed. Some surgical procedures involve both open surgical and endovascular techniques. In general, surgical procedures carry higher risk and longer recoveries but, in some cases, may offer better and longer-lasting outcomes than endovascular procedures. These include:
Endarterectomy. The removal of atherosclerotic plaque from a blood vessel to allow better blood flow through a blocked artery. This is one of the oldest techniques for repairing blood vessels and continues to be used either alone or in combination with other procedures for a large number of patients with peripheral arterial disease (PAD). During this procedure, the atherosclerotic plaque is peeled out of the artery. Once the plaque is removed, the resulting vessel is larger than its original size.
Bypass surgery. This refers to the “rerouting” of blood through a new pathway or bypass graft. A bypass graft that is harvested from the patient’s body is referred to as an autologous conduit or autologous graft. It is almost always a vein taken from the leg but can be an artery. A bypass graft made from an artificial substance, usually polyester or an expanded form of Teflon, is referred to as a prosthetic graft. The graft is sewn to a blood vessel that has a good blood supply and then routed to a normal blood vessel past the blockage. This restores normal blood pressure to the affected leg past the area of the blocked artery.
Gene therapy. An experimental treatment for a variety of different medical conditions. The concept is to introduce cells, or harmless viruses that transport healthy genes, into organs or areas of the body that contain defective or missing DNA. One area of gene therapy is stem cell research. Stem cells are immature cells, meaning they have the ability to develop into a variety of mature cells, such as red or white blood cells, platelets, heart muscle cells, brain cells, etc. Recent studies have reported encouraging findings using stem cells taken from a patient’s own bone marrow. Bone marrow cells are seen to enhance the formation of blood vessels and rebuilding of muscle. Researchers find that bone marrow implanted into the leg can reverse claudication associated with PAD.
Vascular surgeons, interventional cardiologists or radiologists who have been specifically trained in each treatment area may conduct these procedures.
Questions for your doctor
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about lower extremity peripheral arterial disease (PAD):
Why do you think I have lower extremity PAD?
Are all of my symptoms due to my condition, or could there be other conditions also present?
What tests can I expect to determine if I have lower extremity PAD? Will any of these tests require a stay in the hospital or a friend to drive me home?
Where can I go to learn more information?
Do I have any risk factors that might make it more likely that I will develop lower extremity PAD?
Are there any lifestyle changes I can make to reduce my chances of developing lower extremity PAD?
How is my condition treated?
Do you recommend I begin taking or stop taking any medications to improve my lower extremity PAD?
Are there any lifestyle changes I can make to hasten treatment of my lower extremity PAD?
