Like coronary artery disease (CAD), peripheral arterial disease (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 CAD involves the coronary arteries, PAD occurs in arteries outside the heart (e.g., in the kidneys, legs and/or feet). It can also affect the carotid arteries (which supply blood to the brain), increasing the risk of stroke.
There are four major areas where peripheral arterial disease (PAD) produces symptoms:
In the arteries supplying blood to the brain. Cerebrovascular disease (including carotid artery disease) is the number one cause of stroke and disability in the United States.
In the arteries supplying blood to the arteries of the kidneys. PAD of the renal arteries (renal artery stenosis) is one of the causes of high blood pressure and renal failure.
In the arteries supplying blood to the legs. PAD of the lower extremities is a major cause of diminished ability to walk and advanced cases can lead to leg amputation.
In the arteries supplying blood to the intestines. PAD of the mesenteric arteries (mesenteric arterial disease) is less frequent but can cause severe pain, weight loss and death from intestinal gangrene.
A separate condition, abdominal aortic aneurysm (AAA) is also associated with PAD. AAA is the bulging or ballooning out of part of the wall of the abdominal aorta, a section of the blood vessel that carries oxygen-rich blood from the heart to the body.
The diagnosis and treatment of PAD depends on where it occurs and the complications associated with that form of the disease. In the lower extremities, for example, diagnosis of PAD typically involves a painless measurement called an ankle-brachial index (ABI). Elsewhere, the diagnosis may involve the use of more complex testing such as duplex imaging, magnetic resonance angiogram (MRA) and/or an angiogram. If PAD is diagnosed in one part of the body, it's highly likely that other arteries will be affected because atherosclerosis tends to be a systemic disease, or one that affects multiple areas of the body.
Treatment for PAD depends on the symptoms and possible complications. In the legs, where PAD may cause pain and impair the ability to walk, the goal is to restore blood flow to the tissues beyond the blockage. In the neck and head, the goal is to prevent stroke. In general, treatment for PAD often involves new and improved medications (e.g., antiplatelets), risk factor modification and other more specialized measures. More invasive treatments, such as catheter-based procedures and bypass surgery, are also available, depending on where the disease is located.
Like coronary disease, there are both controllable and uncontrollable risk factors for PAD. Risk factors for this condition that are not controllable include gender, age, 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, stress or anger, and high LDL cholesterol and low HDL cholesterol.
About peripheral disease (PAD)
Peripheral arterial disease (PAD) is a type of peripheral vascular disease (PVD) – a group of diseases that affects the body’s blood vessels (arteries, veins and capillaries). Peripheral arterial disease describes all of the conditions that can affect the arteries of the body outside of the heart (within the heart, these conditions are called coronary artery disease or CAD).
The vast majority of PAD conditions are caused by atherosclerosis (“hardening of the arteries”), this process by which plaque deposits slowly form on the inside walls of arteries. Atherosclerosis is also the process responsible for nearly all of the coronary artery disease (CAD) in the United States. CAD, also referred to as heart disease, is the number one cause of death in America. Coronary artery disease is atherosclerosis that occurs in the small coronary arteries supplying the heart muscle with oxygen-rich blood. When these arteries are blocked, the heart muscle dies (heart attack).
PAD is closely linked to CAD because of the nature of atherosclerosis. Researchers have discovered that atherosclerosis is a widespread disease, often present throughout the whole arterial system. When atherosclerosis is discovered in one artery, it is likely present in other arteries. While atherosclerosis in many areas of the body may not be dangerous or produce symptoms, it does create a higher likelihood that significant and dangerous disease exists in more critical areas. For that reason it is important to be aware of all the symptoms and dangers of both cardiac atherosclerosis and peripheral atherosclerosis.
Not all PAD is caused by atherosclerosis. There are a variety of other conditions that may affect the peripheral arteries, but these conditions are responsible for less than 10 percent of all cases of symptomatic PAD. These other causes of PAD include blood clot or embolism, vasculitis (inflammation of the blood vessels), aortic dissection, and tumor (extremely rare).
Atherosclerosis is a degenerative process that occurs in the lining of the arteries. It begins as a small plaque or “blemish” on the wall of the artery called a lesion. In the early stages, this lesion is harmless or benign. As the disease progresses, the lesion grows in both size and complexity, becoming a mixture of cells (e.g. smooth muscle cells, inflammatory cells), cholesterol crystals and calcified tissue. As this mixture grows, there is less room within the artery through which blood can flow. In response, the artery expands to keep the width of the artery normal. When the lesion progresses into its most advanced stages, the artery can no longer expand to accommodate the growing plaque lesion and the plaque begins to narrow the lumen (the space within the artery). This is referred to as stenosis or occlusion of the affected artery.
In addition to blocking the artery, the plaque may become unstable. In this case, there is the increasing possibility that pieces of plaque may break off and travel down the artery (an embolism). These pieces continue to travel until they lodge in a smaller artery and block the flow of the blood to the tissues and organs beyond the blockage. Alternatively, the body may identify the ruptured plaque deposit as an injury and a blood clot can rapidly form over the site. In either case, the supply of oxygen-rich blood will be limited beyond the obstruction, causing the rapid death of tissue and organs.
The consequences of PAD vary greatly based on the artery and organ system it affects. Diagnostic tests to diagnose the location and extent of the disease, as well as appropriate treatments, also differ. It is beneficial to examine the particular area of blood vessels (“circulatory bed”), such as the brain or kidneys, when describing symptoms, testing and treatment.
The major areas where atherosclerosis produces symptoms in the peripheral artery beds are:
Cerebrovascular, or brain arteries (e.g. carotid and vertebral arteries). Cerebrovascular disease (including carotid artery disease) is the number one cause of stroke and disability in the United States.
Renal, or kidney arteries. Renal artery stenosis (PAD of the renal arteries) is a major cause of high blood pressure and renal failure requiring dialysis or transplant.
Lower extremity, or leg arteries. Lower extremity PAD is a major cause of diminished ability to walk. Studies have shown that, perhaps because of differences in leg strength, women with lower extremity PAD tend to have more difficulty walking than men. Advanced cases can lead to gangrene and amputation of the legs.
Mesenteric, or intestinal arteries. PAD of the mesenteric arteries (mesenteric arterial disease) is less frequent but can cause severe pain, weight loss and death from intestinal gangrene.
Another possible consequence of atherosclerotic arterial disease is the formation of an aneurysm. This generally occurs in the aorta, which is the central artery of the body, or the “trunk” of the arterial tree. Aortic aneurysm is a significant cause of death in the United States, with over 15,000 deaths each year. The vast majority of these deaths (more than 95 percent) are preventable if the aneurysm is detected. Unfortunately, aortic aneurysms frequently do not have symptoms, and the first indication is a rupture. Less commonly, an aneurysm can form in the popliteal and femoral arteries of the legs. This generally occurs without warning or prior symptoms
The likelihood of acquiring PAD increases with age. Nearly 20 percent of Americans over the age of 65 have PAD, yet studies have shown that only 25 percent of these patients are undergoing treatment. Researchers believe this low figure is due to the widespread belief that symptoms of PAD are part of the normal aging process. In reality, the vast majority of diagnosed patients are able to control this progressive condition with proper medical treatment.
Cerebrovascular disease
Although there are many kinds of cerebrovascular disease, the term is most often used to describe atherosclerosis that occurs in the blood vessels supplying blood to the brain. About 95 percent of diagnosed cerebrovascular disease occurs within arteries in the neck (carotid arteries), which supply oxygen-rich blood to the brain. This form of PAD is called carotid artery disease.
Lower extremity PAD
Lower extremity PAD 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.
Renal artery stenosis
Peripheral arterial disease of the renal arteries (often referred to as renal artery stenosis) is usually atherosclerosis that occurs in the blood vessels leading to the kidneys. The primary function of the kidneys is to filter the blood and remove waste products and excess fluids. For that reason the kidneys receive almost one-third of the blood flow of the body. They play a major role in regulating blood pressure. If the narrowing in the renal artery is significant, the kidney incorrectly senses that the blood pressure is too low and sends signals to the body to increase the blood pressure resulting in high blood pressure (hypertension). This is generally referred to as renovascular hypertension and can accelerate the progression of atherosclerosis throughout the body, increasing the strain on the heart.
Renal artery stenosis can also result in poor renal function (renal insufficiency), which impairs the waste and fluid removal functions of the kidney. Renal insufficiency can eventually lead to the need for dialysis as a replacement for kidney function.
Mesenteric arterial disease
Mesenteric arterial disease refers to diseases that affect the blood vessels supplying the intestines and other abdominal organs (e.g., the belly). Because the blood vessels supplying this part of the body are so numerous, blockages of these arteries are the least likely to result in a condition requiring treatment.
Abdominal aortic aneurysm
An abdominal aortic aneurysm (AAA) is the dilation, bulging or ballooning out of part of the wall of the abdominal aorta, a section of the aorta that travels the entire length of the abdomen. An aneurysm rupture can result in massive bleeding and often death with mortality rates between 70 percent and 90 percent. Moreover, these aneurysms often have no symptoms. Therefore early diagnosis and treatment of an aortic aneurysm is vital to preventing an aortic rupture.
Prevention methods for PAD
Non-surgical strategies to control PAD are similar to those that prevent coronary artery disease. These include:
Quitting smoking (or not starting to smoke). Tobacco smoking is a major cause of peripheral arterial disease and stroke. Smokers who develop PAD are diagnosed with the condition about 10 years earlier than nonsmokers. According to the U.S. Centers for Disease Control and Prevention (CDC), heart disease is the leading smoking-related cause of death in the United States among men and women. The CDC also suggests that the average smoker dies nearly seven years before a nonsmoker. Experts say that quitting smoking is probably the most important step toward reducing the risk for PAD.
Eating a heart-healthy diet. Modern research has consistently supported the idea that the health of people’s bodies is largely determined by what they choose to eat. While certain vitamins and minerals have been shown to be helpful to heart health, fats and oils such as saturated fat and tropical oils (palm and coconut oil) have been shown to be particularly harmful, because they can speed the development of peripheral arterial disease, atherosclerosis and obesity.
Improving your cholesterol profile. A person’s total cholesterol (which includes LDL cholesterol, HDL cholesterol and triglycerides) should be no more than 200 milligrams per deciliter (mg/dL). Key strategies for reducing levels of total cholesterol, LDL cholesterol and triglycerides are to eat a heart-healthy diet and to exercise regularly. If these strategies do not reduce total cholesterol levels, a physician may prescribe cholesterol-reducing drugs. Strategies for increasing levels of HDL cholesterol include eating monounsaturated fats in moderation, decreasing the amount of saturated fat, limiting alcohol use and starting an exercise program (under a physician’s supervision).
Controlling homocysteine levels. Homocysteine is an amino acid produced as a normal byproduct of protein metabolism. High homocysteine levels have been linked to damage of the arteries, which may increase the risk of heart attack, stroke or other cardiovascular problems. Researchers are studying whether high homocysteine levels are an actual cause of such conditions, or are simply associated with them for some other reason. The American Heart Association recommends testing homocysteine blood levels in patients with known risk factors for heart disease (e.g., a family history of heart disease). Homocysteine can be kept at moderate, healthy levels if the body has adequate levels of three important B-vitamins: vitamin B6, vitamin B12 and folic acid (the synthetic and more easily absorbed version of folate). Therefore people are encouraged to make sure they get enough B-vitamins every day.
Exercising regularly. Exercise can be an excellent tool in both prevention of heart disease and improving quality of life for heart patients. Physically, it can slow or even reverse the process of atherosclerosis, as well as lower blood pressure and reduce cholesterol levels. Emotionally, it can reduce levels of stress and depression. Individuals should consult with a physician before beginning an exercise program.
Controlling diabetes. Persons with diabetes are more likely to develop heart-related diseases. Preventative care is crucial to the overall health and heart function of diabetic patients.
Controlling high blood pressure (hypertension). Individuals with high blood pressure are at greater risk of cardiovascular problems resulting from CAD. Hypertension can be controlled through taking blood pressure medications, self-monitoring, eating a heart-healthy, low-salt diet and engaging in regular exercise. People are also encouraged to have regular check-ups with their physician.
Controlling weight. Obesity and being overweight are major risk factors for a host of serious health conditions, including peripheral arterial disease, high blood pressure, diabetes, heart attack and stroke. Some weight control methods include limiting fat in a patient’s diet, increase activity levels, counseling, medication and surgical interventions.
Stress management. Stress can lead to high-risk practices such as overeating, smoking, high blood pressure (hypertension) and a lack of exercise. In addition, chronic stress may be a direct contributor to poor heart health because it produces increases in blood pressure that could become permanent.
Controlling chronic depression. Depression has been linked with a higher risk of developing high blood pressure, heart disease and having a heart attack.
Learn your family medical history. A patient’s family medical history can greatly increase (or decrease) the risk of the patient developing certain medical conditions, including peripheral arterial disease. Some patients prefer to develop their own medical family tree and bring it with them to their doctor appointment. A complete family tree traces the medical history of an individual (and his or her spouse, if applicable), through at least several generations.
Recent research regarding PAD
Research into the causes of peripheral arterial disease (PAD), as well as potential methods of diagnosis and treatment, is ongoing. Recent findings include:
Drug-eluting stents. Like coronary artery disease, PAD can be treated with the combination of balloon angioplasty and stenting. During this procedure, a balloon-tipped catheter is threaded to the site of the obstruction and the balloon is rapidly expanded, crushing the plaque against the arterial wall. At the same time, a tiny mesh tube called a stent is permanently implanted in the artery to keep it open. Newer stents are coated with special drugs that help reduce the rate of reclosure, or restenosis. These medicated stents are being tested for the treatment of PAD and are not currently available in the United States.
Photoangioplasty. A new combination drug and laser therapy that may prove to be an effective treatment option in the future. The procedure is no more invasive than standard balloon angioplasty. A drug called texaphyrin (TEX–a–frin) is injected directly into the patient’s veins about 24 hours before the procedure. Once in the bloodstream, the drug attaches itself to areas of fatty plaque buildup. For the procedure, a fiber–optic laser threaded through the body via a catheter and into the affected areas. Once in the target area, the laser is activated and its light triggers a reaction in the drug that dissolves the plaque. Photoangioplasty is currently being tested for use in the treatment of PAD.
Blood testing. New blood tests, including specialized lipoprotein testing, are helping researchers to better identify people at risk from abnormal cholesterol levels. While these tests are being used mainly for identifying coronary artery disease, they can still be helpful in identifying people at elevated risk of atherosclerosis anywhere in the body. Similarly, C-reactive protein, which indicates inflammation somewhere in the body, is a blood marker that has been studied extensively in relation to heart disease risk.
Gene therapy. Researchers are exploring ways to transform certain tissue cells into more specialized cells. For example, some studies have injected a patient’s own bone marrow in the legs in order to trigger the growth of new blood vessels.
Drugs. Researchers continue to work on the development of drugs or drug combinations that can help reduce the symptoms and consequences of PAD. Some clinical trials have paired drugs with forms of exercise and studied their effect on functional skills and progression of the disease.
Questions for your doctor regarding PAD
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 peripheral arterial disease (PAD):
What may have caused my PAD?
What arteries and organs are affected by this condition?
How severe is my PAD?
What diagnostic tests will be necessary?
How will they be performed?
What complications can I expect from my PAD?
What are my treatment options for this condition?
What are the benefits and risks with these treatments?
What are the chances that my PAD will become worse?
What symptoms from the PAD indicate a medical emergency?
