Leg Pain and Peripheral Arterial Disease (PAD)
What Is Lower Extremity Peripheral Arterial Disease (PAD)
The inner lining of arterial blood vessels is normally smooth, allowing blood to flow easily. In lower extremity PAD, the lining becomes damaged, leading to buildup of cholesterol and other lipids, causing the arterial wall inner lining to become rough and thickened. This accumulation is called atherosclerosis, or "hardening of the arteries." As the atherosclerotic process of the lower extremity arteries increases, the arteries become narrowed or blocked, causing blood flow to decrease. This can lead to discomfort, cramps, or pain in the hips, thighs or calves with walking. This is called claudication.
Claudication typically occurs during physical activity such as walking and is promptly relieved by a brief resting period (2-5 minutes).Normally, blood flow can increase up to ten-fold to meet the increased need for additional oxygen in exercising muscles. However, when the leg arteries are blocked, blood flow cannot increase in response to exercise and pain develops.
Claudication pain always involves the same muscle groups, usually the calves, and does not change from day to day. The vascular surgeon relates the onset of claudication pain to a particular walking distance in terms of street blocks (e.g. "2-block claudication") or distance traveled before the symptom occurs. This helps to provide a standard of measuring if there has been any change before and after therapy has been initiated.
As atherosclerosis progresses and blockage becomes more severe, pain may occur in the feet even when at rest. This pain, known as rest pain, occurs because the arteries of the leg can no longer deliver adequate blood flow to the feet, even at rest. Rest pain generally worsens when the legs are elevated, such as when lying in bed at night. Relief from this pain may occur only when the feet are dangled. Gangrene or "death of tissue" may occur when nutrition needed for normal growth and repair can no longer be provided because of extensive arterial narrowing (stenosis) or complete blockage (occlusion) of lower extremity arteries.
Currently, atherosclerosis affects up to 10% of the Western population 65 years or older. When claudication is used as an indicator of lower extremity arterial disease, estimates are that 2% of the population aged 40 to 60 years and 6% older than 70 years of age are affected. With the elderly population expected to increase to 22% by the year 2040, lower extremity arterial disease will be even more common.
The risk factors for atherosclerosis affecting the lower extremities are the same risk factors associated with coronary artery disease or cerebrovascular disease. These risk factors include:
- High blood pressure (hypertension)
- High levels of blood cholesterol or triglycerides (hypercholesterolemia, hyperlipidemia)
- Sedentary lifestyle
- Family history of heart disease or arterial disease
Smoking is the most influential of all the risk factors. Although the mechanism by which smoking causes or worsens atherosclerosis is unclear, it is known that the degree of damage to the arterial wall lining is directly related to the amount of tobacco used. Quitting smoking is essential in the battle against atherosclerosis progression.
Signs and Symptoms
Essential to the management of a patient with leg pain is a comprehensive lower extremity examination including palpation of peripheral pulses. Signs and symptoms that advanced lower extremity arterial disease is causing the leg pain include:
- Decreased hair growth on the legs and feet
- Discoloration of the affected leg or foot when dangling (from pale to bluish-red)
- Diminished or absent pulses in the affected leg or foot
- Temperature difference in affected leg or foot (cooler than other extremity)
- Change in sensation (numbness, tingling, cramping, pain)
- Presence of non-healing wound on affected lower extremity
- Shrinking of calf muscles
- Presence of thickened toenails
- Development of gangrene
Other Diseases That Must Be Considered
Other disorders can cause leg pain including:
- Arthritis - Arthritic pain is variable from day to day and may be aggravated by certain weather patterns or physical movements. Unlike claudication, rest does not provide relief.
- Varicose veins - The pain associated with varicose veins is a dull aching, typically occurring at the end of the day or after prolonged periods of standing. Pain from venous disease is not exacerbated by exercise.
- Venous thrombosis - Swelling and leg pain associated with venous thrombosis typically occurs with walking and is relieved by extremity elevation, unlike arterial disease.
- Spinal stenosis - narrowing of the spinal canal due to a ruptured disk or arthritis of the back causes leg pain when standing and is not relieved by brief resting periods. Relief of pain often occurs by leaning forward against a stationary object (e.g. a tree) or sitting.
- Diabetic Neuropathy - Pain associated with this complication of diabetes is usually present in both legs. It often presents with numbness and diminished sensation in the lower extremities.
If you are suspected of having lower extremity arterial disease or your symptoms are worsening, the vascular surgeon will ask you certain questions, examine you, and order either non-invasive or invasive diagnostic tests.
- Non-invasive testing: These tests are performed in the clinic setting or in a vascular laboratory, most often on an outpatient basis. They are virtually painless methods of examining the blood flow to the extremities, with essentially no side effects or risks.
- PULSE EXAMINATION: This is the primary assessment of the circulation. Normal findings by an experienced examiner make the likelihood of lower extremity arterial disease remote.
- ARTERIAL BLOOD PRESSURES: Using an ultrasound stethoscope (Doppler), the blood pressure in your arms and legs is measured , and the pressures are compared. This test gives the vascular surgeon a generalized assessment of the severity of the lower extremity arterial disease.
- DUPLEX SCANNING: This test is useful for detecting blockages in an artery and measuring the size of the artery. It may also be used to measure the size of a vein that may be used as a bypass, a means of re-routing blood flow around a blocked or occluded area.
- MAGNETIC RESONANCE ANGIOGRAPHY (MRA) or COMPUTED TOMOGRAPHIC ANGIOGRAPHY (CTA): This test is also useful for imaging extremity vessels.
- Invasive Testing: Tests in this category involve the injection of a contrast dye directly into your arteries under X-ray guidance.
- Angiogram: This test is the most helpful imaging study used to direct treatment of symptomatic lower extremity arterial disease. Dye is injected directly into the artery and special x-rays are taken to reveal the exact location of the arterial blockage. An angiogram is only necessary when interventional or surgical treatment is being considered.
The treatment of leg pain due to claudication is primarily medical management of the symptoms and exercise, with surgery reserved for severe exercise induced pain which negatively impacts an individual's lifestyle. While atherosclerosis can not be totally cured or prevented, the progression of the disease can be controlled through risk factor modification. This involves changing one's lifestyle to include healthy habits.
- SMOKING: Tobacco in any form should be avoided. Continued cigarette smoking is the most consistent adverse risk factor associated with progression of lower extremity arterial disease in patients experiencing claudication. The nicotine found in tobacco products causes the blood vessels to constrict, further narrowing them, preventing blood from reaching the intended targets (e.g. body organs, extremities), increasing the risk of atherosclerosis. In addition, smoking also decreases the amount of oxygen in the blood and can cause the blood to clot more readily.
- HIGH BLOOD PRESSURE: Untreated or uncontrolled high blood pressure (hypertension) causes the heart to work harder and creates additional stress on the arteries. Blood pressure should be monitored regularly because often hypertension occurs without symptoms. Take your medications as prescribed as long as your physician instructs you to, even if it normalizes and you "feel good."
- DIET: The risk of atherosclerosis can also be reduced by carefully monitoring cholesterol (found in organ and red meats, diary products and egg yolk) and saturated fats (found in animal fat and plant oils) in the diet. Polyunsaturated fats (found in corn, safflower and olive oils) are the fats to incorporate in your diet. In addition, a salt-restricted diet will help control high blood pressure and fluid retention associated with weight gain. If you are overweight, a general weight reduction diet is advantageous. Checkups with the doctor should include the monitoring of serum cholesterol. If it remains high (>200) despite the above diet then medication to reduce the cholesterol should be considered.
- EXERCISE: Exercise plays a vital role in the treatment of atherosclerosis in patients with claudication. Patients with intermittent claudication often voluntarily reduce their daily walking because of pain and the fear of causing further tissue damage. This leads to an increasingly sedentary lifestyle that complicates the picture even more. Increase your walking distance gradually, stopping to rest when the leg pain develops. When it disappears, begin walking again. Measurable improvement ranged from 80-234% in controlled studies that incorporated a regular walking program into the daily routine. A regular walking program of 45-60 minutes/day is recommended.
- DIABETES: Due to the important role that diabetes mellitus plays in the earlier onset and accelerated rate of atherosclerosis progression, it is crucial to follow the advice of the health care team regarding diet, medications, and treatment. Early treatment and meticulous management is paramount to controlling the effects of diabetes on arteries.
- FOOT CARE: When blood flow to the lower extremities is decreased, delayed healing of sores, serious infections, and gangrene (tissue death) of the feet or toes can occur after seemingly minor injuries (e.g. hang-nail, superficial laceration). Care must be given to avoid any situation that might cause injury to the foot. Inspect your feet daily. Immediately report to your physician the detection of any foot injuries or sores.
- PHARMACOLOGIC THERAPY: In addition to others prescribed by your physician, the following medications may be added to your regimen:
- Anti-Platelet Agents - These drugs decrease the overall risk of heart attacks (angina, myocardial infarction) or strokes (cerebrovascular accidents or transient ischemic attacks) in persons with atherosclerosis. They also may improve walking distance by enhancing blood flow and overall circulation. Two examples of anti-platelet agents are:
- Aspirin - One aspirin tablet (81-325 mg) daily is the main antiplatelet agent utilized.
- Clopidogrel bisulfate (Plavix®) - Plavix is a newer anti-platelet agent that appears to be gaining in popularity. Studies are in the process of determining which patient populations would most benefit from using this agent.
Anticoagulation Agents - These drugs inhibit clot formation. Examples of these medications include:
- Warfarin (Coumadin®) - The amount of this pill that is prescribed is based on specific blood test results.
- Lovenox® - This medication, given as an injection, is used to achieve adequate anticoagulation, often while waiting for the warfarin dose to reach a therapeutic level.
- Other Agents - These medications improve the circulation in the lower extremity. Treatment for at least one month is required to produce noticeable results. Examples of these types of medications include:
Surgical and Endovascular Management
In cases where diligent medical therapy is not sufficient in resolving the symptoms or the symptoms progress at a very fast rate and have become lifestyle restricting, surgical therapy should be considered.
The first in providing surgical care is to determine exact location of the arterial blockage in the leg. Although this can be performed with an ultrasound, the most accurate test is called an arteriogram. An arteriogram is an outpatient procedure where a small needle and catheter are inserted into your artery. It is similar to having an IV started. A biologically safe dye is then injected into the arteries and pictures are taken of the blood flowing down each leg. This provides a roadmap of all of the normal and abnormal segments of arteries and allows the surgeon to identify the areas of concern.
Once the areas of arterial blockage is determined, two treatments options are possible; angioplasty and stenting or open surgery.
a) Schematic of balloon angioplasty catheter positioned through stenotic iliac lesion. b) Balloon inflates, dilating arterial narrowing. c) When stenosis is dilated, balloon angioplasty catheter deflates. d) Illustration shows remote percutaneous femoral access and balloon catheter placement through stenotic iliac artery.
An angioplasty is when small balloon is used to dilate a narrowed segment of an artery. Typically, the balloon is inserted into the artery and placed exactly at the area of arterial narrowing. The balloon is then inflated; smashing the plaque that was inhibiting the blood flow. Stents are frequently used in combination with angioplasty to optimize the results. The stents hold the vessel open and trap the plaque against the arterial wall. This procedure can be performed at the same time as the arteriogram and usually requires less than a 24-hour hospital stay.
If there is too much blockage in the arteries to treat with balloon angioplasty and stent, an open bypass operation must be undertaken. A bypass operation involves finding a suitable blood vessel above and below the area of blockage and routing blood flow between the two vessels with the aid of a bridge (graft) carry the blood between the two vessels. The graft may be constructed from a vein in the leg or a synthetic material. The procedure usually requires 2 to 5 hours of surgery. A hospital stay of 3 to 7 days after surgery can be anticipated. A blood transfusion is needed in less than 10% of cases.
Angioplasty and open surgical repair are very safe procedures with excellent results. Factors that may diminish the success of each procedure include:
- the amount of arterial blockage present,
- the overall health status of the patient and,
- adherence to risk factor control after the intervention.
The most significant risk factor that contributes to early failure after intervention is smoking; therefore lifelong cessation is paramount.
Patients with lower extremity arterial disease may present with symptoms ranging from minor claudication to extensive gangrene and threatened limb loss (amputation). While studies of large groups of patients with claudication reveal that amputation is uncommon, it continues to be a significant fear. How rapidly arterial disease progresses to limb loss largely depends on the number and severity of risk factors (e.g. smoking, hypertension, obesity, diabetes). Timely and regular medical evaluations and patient compliance with smoking cessation, diet and blood pressure control, daily exercise, and adherence to prescribed treatment modalities can markedly improve the claudication symptoms and ultimate outcome associated with lower extremity arterial disease.