Blood supply to the limbs occurs via the peripheral arteries of the body. Peripheral arterial disease (abbreviated as PAD) refers to impaired blood flow to the limbs through the peripheral arteries. The impaired blood flow is mainly caused by a narrowing of the lumen of these arteries. Peripheral arterial disease is a serious condition that can lead to limb amputations if not treated promptly.
Blockage of peripheral arteries starves the limb tissue of oxygen. Limb tissue may undergo necrosis due to acute limb ischemia caused by peripheral artery disease. Left untreated, gangrene may form in the affected limb. Limb amputation is usually required at this stage to prevent the spread of gangrene. Even though both the arms and legs can get affected by peripheral arterial disease, the condition is more common in the lower limbs. The rise of atherosclerosis in the present day world is causing a global increase in the incidence of peripheral arterial disease.
Read more on atherosclerosis.
Signs and Symptoms
In the initial stages of peripheral arterial disease, there may not be any overt signs or symptoms. The symptom-free phase may extend for many months. One of the first symptoms of peripheral arterial disease is a muscular pain that may arise in the legs after short walks. This pain is caused by tissue injury that results from an occlusion of the peripheral artery. Resting for a short time eases the pain in the lower limbs.
This pain (medically referred to as intermittent claudication) usually affects only one of the legs (unilateral pain). If both legs are affected by intermittent claudication, one may suspect an occlusion of the lower part of the abdominal aorta. Intermittent claudication may progress to pain in the legs that occurs even at rest. This type of pain (referred to as ischemic rest pain) worsens while lying down since the blood flow through the occluded arteries is no longer aided by gravity.
Apart from intermittent claudication and ischemic rest pain in the lower limbs, there may be other signs and symptoms that suggest the presence of peripheral arterial disease. The following are some of the common symptoms that may occur:
- The color and texture of the skin on the legs may change. The skin may become dry, shiny and pale in color.
- Muscle weakness may occur in the affected limbs.
- Abnormal sensations such as itching, numbness and tingling may occur in the affected legs.
- The skin on the affected leg may lose hair.
- Arterial pulse in the affected limb may be weak or absent.
- Ulcers may develop in the affected limb.
- The temperature of the skin on the affected limb may drop.
Read more on leg pain.
Causes of Peripheral Arterial Disease
The main cause of peripheral arterial disease is reduced blood flow through the peripheral arteries. This reduction in peripheral arterial circulation of blood may occur due to two main causes – atherosclerosis and presence of blood clots. These conditions narrow the lumen of the peripheral arteries, causing a reduction or stoppage of blood flow to the limbs.
In the modern times, atherosclerosis has become a major cause of circulatory diseases, including peripheral artery disease. Atherosclerosis is characterized by the formation of cholesterol-containing plaques inside the lumen of the arteries. These plaques build up gradually within the arteries over a period of time.
Consequently, the lumen of the peripheral arteries narrow and the flow of blood through them becomes increasingly restricted. Smoking, hypercholesterolemia, diabetes mellitus, and hypertension are some of the risk factors for developing atherosclerosis.
Restricted blood flow through the peripheral arteries can also occur due to the presence of blood clots in these arteries. Blood clots may either stay at the site of their formation or break away from their original site to obstruct blood flow elsewhere in the circulatory system. A blood clot that stays at its site of formation is known as a thrombus, whereas a breakaway clot that clogs the bloodstream elsewhere in the circulatory system is known as an embolus.
Peripheral arterial disease can be caused by both a thrombus that forms in the peripheral arteries and emboli that reach the peripheral arteries from other parts of the circulatory system. Thrombus formation occurs due to irregularities in the blood vessels. A turbulent flow of blood through such irregular blood vessels causes platelets and blood cells to stick and cause clot formation.
A thrombus can grow at a rapid rate and cause peripheral arterial disease faster than atherosclerosis can. Therefore, the symptoms of peripheral arterial disease may appear quicker in the case of a thrombus than in case of atherosclerosis. An embolus is the most rapid cause of peripheral arterial disease. Breakaway clots that get dislodged from their original site may cause complete obstruction of blood flow when they get stuck in the narrow peripheral arteries of the legs.
A common site of blockage caused by embolus is the femoral artery. Unlike atherosclerosis and thrombus formation, blockage of blood flow by emboli can cause a sudden appearance of symptoms. If an embolus manages to block the blood flow through major arteries, serious consequences may ensue. Blockage of minor peripheral arteries may still allow blood flow to occur via alternate routes and cause minimal damage.
Diagnosing Peripheral Arterial Disease
One may suspect the presence of peripheral arterial disease by looking at the tell-tale signs and symptoms of the disease in an individual. However, confirmed diagnosis requires clinical examination. The following clinical studies may be done to confirm a diagnosis of peripheral arterial disease:
The flow of blood through the lower limbs can be studied using ultrasound. This is usually the first prescribed test because of its non-invasive nature.
If adequate facilities are available, then one might go for angiography (magnetic resonance angiography or computerized tomographic angiography) to study the flow of blood through the peripheral arteries in the legs. Angiography can provide a detailed picture of the site of blockage in the peripheral arteries.
Treating Peripheral Arterial Disease
Peripheral arterial disease can be treated through medications and surgery. Medications are typically given to treat the underlying causes of peripheral arterial disease, such as diabetes, hypercholesterolemia, hypertension, and blood clots.
Surgical procedures such as balloon angioplasty and arterial bypass surgery may also be done to restore blood circulation in the affected limbs. Apart from immediate treatment measures, some lifestyle changes such as cessation of smoking, avoiding unhealthy foods and exercising regularly are also required to manage the condition in the long term.