Arteries and veins have the same layers of tissues in their walls, but the proportions of these layers differ. Lining the core of each is a thin layer of endothelium, and covering each is a sheath of connective tissue, but an artery has thick intermediate layers of elastic and muscular fibre, while in the vein these are much thinner and less developed. With the exception of pulmonary and umbilical veins and arteries, arteries carry oxygenated blood from the heart, while veins return deoxygenated blood to the heart. The thicker and more muscular walls of arteries help them to withstand and absorb the pressure waves which begin in the heart and are transmitted by the blood. The arterial wall expands and swells with the force of each contraction of the heart, then snaps back to push the blood forward as the heart rests. From the arteries, blood enters smaller branches of arteries
called arterioles and then the capillary network. Just as arterioles are smaller branches of arteries, so venules are smaller branches of veins. Venules receive blood from the capillaries and branch into veins that return blood to the heart. They do not have the need for the strength and elasticity of the arteries, so the walls of the veins are thin and almost floppy. To
make up for this, many veins are located in the skeletal muscles, and the least movement of a limb squeezes the vein and drives the blood toward the heart. One‐way valves ensure flow in the right direction.
Pathophysiology
PAD is a common condition in which a build‐up of fatty deposits in the arteries restricts blood supply to leg muscles. It is also known as PVD. PVD is a cardiovascular disease, meaning it affects blood vessels. It is usually caused by a build‐up of fatty deposits in the
walls of the leg arteries. The fatty deposits, called atheroma, are made up of cholesterol and other waste substances. The narrowing of the arteries is caused by atheroma. A patch of atheroma starts quite small, and causes no problems at first. Over the years, a patch of atheroma can become thicker . (It is a bit like scale that forms on the inside of water pipes.)
What causes atheroma?
There are many risk factors associated with PVD and they include smoking, obesity, hypertension, excessive alcohol consumption, men are at higher risk than women, familial history and ethnic group (for example people who live in the UK, with ancestry from India, Pakistan, Bangladesh or Sri Lanka, have an increased risk). Some risk factors are more risky than others. For example, smoking causes a greater risk to health than obesity. Also, risk factors interact. So, having two or more risk factors gives an increased risk
compared with a person who only has one risk factor. For example,a middle‐aged male smoker who does little physical activity and has a strong family history of heart disease has quite a high risk of developing a cardiovascular disease such as a heart attack, stroke or PAD
before the age of 60 years.
Signs and symptoms
The typical symptom is pain, which develops in one or both calves during walking or exercise and is relieved after resting for a few minutes. This pain varies between cases and there may be aching, cramping or tiredness in the legs. This is called intermittent
1.claudication. It is due to narrowing of one (or more) of the arteries in the leg. The most common artery affected is the femoral artery. When walking, the calf muscles need an extra blood and
2.oxygen supply. The narrowed artery cannot deliver the extra blood and so pain occurs from the oxygen‐starved muscles. The pain comes on more rapidly when walking up a hill or stairs than when on the flat. If an artery higher upstream is narrowed, such as the iliac artery or aorta, then the person may develop pain in the thighs or buttocks when they walk. If the blood supply is very much reduced, then the person may develop pain even at rest, particularly at night when the legs are raised in bed. Typically, rest pain first develops in the toes and feet rather than in the calves. Ulcers (sores) may develop on the skin of the feet or lower leg if the blood supply to the skin is poor.
In a small number of cases, gangrene (death of tissue) of a foot may result.
Management
Pain control is paramount in patients with arterial insufficiency. If pain is caused by exercise, such as walking long distances, then they should be advised against it. However, light exercise which they can tolerate should be encouraged as it helps to improve circulation. Patients should be advised to keep themselves warm if they are affected by cold weather, but they should avoid tight fitting clothing, smoking, cold temperatures and
- sitting crossed‐legged for too long.
Patients may need medications such as beta blockers, anticoagulants,
lipid‐lowering drugs and antiplatelet drugs. NICE recommends
naftidrofuryl oxalate for the treatment of intermittent
claudication for PAD. Naftidrofuryl oxalate improves blood flow
in the body.
Surgery
There are two main types of surgical treatment for PAD:
- angioplasty – where a blocked or narrowed section of artery is
widened by inflating a tiny balloon inside the vessel; and bypass
graft – where blood vessels are taken from another part of the
body and used to bypass the blockage in an artery.
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