Peripheral artery disease

Peripheral arterial disease occurs when plaque builds up in the arteries that carry blood to the head, organs, and limbs. This problem occurs when fatty material (plaque) builds up on the walls of the arteries. This causes the arteries to become narrower.

Peripheral artery disease usually affects the legs, but also can affect the arteries that carry blood from patient’s heart to his head, arms, kidneys, and stomach.

Atherosclerosis is a common cause of peripheral artery disease, especially to older people wherein it is a condition in which fatty deposits build up on the inside walls of the arteries, that reduces blood flow, which becomes more common with aging.

Peripheral artery disease can cause discomfort or pain when the patient walk. The pain can occur in the patient hips, buttocks, thighs, knees, shins, or upper feet. These symptoms usually appear during walking or exercise and go away after several minutes of rest.

Leg artery disease is considered a type of peripheral arterial disease because it affects the arteries, blood vessels that carry blood away from heart to limbs.

Peripheral arterial disease affects 8 to 12 million people in the United States. African Americans are more than twice as likely as Caucasians to have peripheral arterial disease. The major risk factors for peripheral arterial disease smoking, age, and having certain diseases or conditions.

The prevalence of peripheral arterial disease increases sharply with age, from 3% in patients younger than 60 years of age to 20% inpatients older than 75 years of age.
Peripheral artery disease

Blood vessel – arteries

The vessels which carry the blood away from the heart are arteries, and arterioles. While the vessels which carry the blood back to heart are veinules and vein.

Arteries are brighter, since they transport blood rich in oxygen to the organs of the body. The veins afterwards transport the blood, which is at a low oxygen level and thus darker, to the lungs and the liver.

Arteries are elastic vessels that are very strong, able to carry blood away from the heart under high pressure. They subdivide into thinner tubers that give rise to branched, finer arterioles.

Blood vessels are made up of three distinct layers called tunics. These are:
❑ Tunica interna/intima (internal layer- epithelial lining)
❑ Tunica media (middle lining- smooth muscles+ elastic connective tissue)
❑ Tunica externa/adventitia (outer lining – connective tissue)

Tunica interna is made up of a layer of simple squamos epithelium known as endothelium. It rests on a connective tissue membrane with many elastic, collagenous fibers. Tunica media makes up most of an arterial wall including smooth muscle fibers and a thick elastic connective tissue layer. The tunica adventitia is composed of collagen and elastic fibers.

The thickness and histologic composition of these three layers differs in arteries, capillaries and veins giving them their unique structure which enables them to perform their unique functions.

The tunica intima and tunica media of elastic arteries are generally thicker than those of the other types, and the tunica media contains elastic fibers. Capillaries differ in that they have a very thin tunica adventitia and their endothelial cells are fenestrated to increase their permeability.

Arteries are classified into three types on the basis of their diameter:
 Elastic arteries/ Conducting arteries
 Muscular arteries/distributing arteries
 Small arteries/ Resistance arteries
Blood vessel – arteries

What is plaque?

Plaque is a fatty material made up of fat, cholesterol, calcium, and other particles found in the blood. Scar tissue and calcium from vessel injury can also add to the plaque buildup. The process leading to this may begin in childhood. It takes decades before it causes serious health problems.

A piece of plaque can break off and be carried by the bloodstream until it gets stuck. Over time, plaque hardens and narrows the arteries. The plaque makes arteries less flexible, a condition called atherosclerosis or “hardening of the arteries.”

Early observations that cholesterol is a key component of arterial plaques gave rise to the cholesterol hypothesis for the pathogenesis of atherosclerosis.

This process can happen to blood vessels anywhere in the body, including those of the heart, which are called the coronary arteries. If the coronary arteries become partly blocked by plaque, then the blood may not be able to bring enough oxygen and nutrients to the heart muscle. This can cause chest pain, or angina. If an artery supplying oxygen to the extremities (often the legs) is blocked, gangrene, or tissue death, can result.

There are often no signs or symptoms of high blood cholesterol. A high level of cholesterol in the blood is due to abnormal levels of lipoproteins. These are the particles that carry cholesterol in the bloodstream. This may be related to:
• Diet
• Weight
• Lack of physical activity
• Genetic factors and
• Presence of other diseases (diabetes, underactive thyroid, etc.)

Smoking makes fatty deposits more likely to form, and it accelerates the growth of plaque.
What is plaque?