Lower Limb Arterial Disease
In order for us to understand leg arterial disease, we need to understand where the arteries travel to and what happens to them.
Read more about the anatomy
The major artery that leaves the heart is the aorta. This large vessel travels through the chest and abdomen giving off smaller branches to supply oxygen and nutrients to the lungs, chest wall, intestines, organs and kidneys. It then divides above the pelvis into two arteries named the common iliac arteries. These arteries each give off a branch - the internal iliac arteries, which via various branches, supply the pelvic area. After giving off this internal iliac arteries the vessels are known as the external iliac arteries and they travel down to supply each limb.
As the vessel reaches the thigh, it is known as the common femoral artery. This artery gives off a deep branch, the profunda femoral artery, and then continues down the thigh as the superficial femoral artery. These arteries supply oxygen and nutrients to the thigh muscles.
As the artery travels behind the knee it is known as the popliteal artery, and below the knee the artery divides into 3 branches, the anterior tibial artery, the posterior tibial artery and the peroneal artery. These latter 3 supply oxygen and nutrients to the muscles in the calf and foot.
The tibial arteries cross the ankle and it is these pulses that you can normally feel on the top of your foot and behind the inside of your ankle. Blockages of the arteries can occur at any level:
- Iliac arteries
- Femoral arteries
- Popliteal arteries
- Tibial and peroneal arteries
Blockages cause the narrowing of the arteries or ‘stenoses’ which then reduce the amount of blood supply to the muscle, nerves and skin of the thigh, calf or foot. Blockages typically occur from the build up of plaque or atherosclerosis. There may be other causes of blockages but these are less common.
Some people may have plaque in their blood vessels but are unaware of it. There are two reasons for this-
- When a stenosis develops, smaller blood vessels known as collateral blood vessels open up to bypass the blockage. Although these collateral vessels can now deliver more blood to the limb they are never quite as good as the original vessel.
- The person may not be active enough to experience the symtpoms of blockages.
Read more about the different symptoms
Different Grades of Disease
|Organ (Cells)||Oxygen delivery decreased||Oxygen delivery critically decreased|
|Heart||Chest Pain||Heart Attack|
|Brain||Minor, reversable stroke||Major Stroke|
|Legs||Pain when walking, Pain when resting||Ulceration, Gangrene|
|Kidneys||High Blood Pressure||Kidney dysfunction|
Mild / Moderate Disease
People who have limb arterial disease with no symptoms are known to have Asymptomatic disease. Although this group of people have no symptoms they are still at a higher risk than the general population of having any vascular event – heart attack, stroke, leg pain or even amputation. What is also important to note is that the reason they do not experience symptoms may be because they are not active enough to experience symptoms. So this makes them unaware of their disease.
We mentioned previously that the arteries to the limbs supply the muscles. If those muscles are used (walking or running) then an increased amount of blood needs to be delivered to these active muscles to provide enough oxygen and glucose for them to function.
People who have blockages reach a point where they cannot supply enough blood for muscles to work and they can get pain or cramp in the muscles from a build up of lactic acid (this happens with anaerobic metabolism – when the muscle tries to function without oxygen).
If you run too far you eventually need to stop because your muscles won’t allow you to go further because you are not supplying enough oxygen to the muscles. The same process happens to some people when they walk because they are starting off with a decreased delivery of blood to the supply due to blockages. These people get the same muscle cramps when they walk as most people do when they run too far. They then stop and rest and the blood can once again be delivered to the muscles and the pain is relieved. This pain is known as Claudication. Claudication means ‘to limp’. It comes form the latin word claudus meaning ‘lame’ or ‘crippled’. It can usually be managed by medical means – that is optimal control of risk factors for atherosclerotic plaques. Rarely does it require surgery.
People with Asymptomatic disease or Claudication require medical management. This medical management is seldom optimised or followed up sufficiently and even more seldomly individualised. Simply being on medications is not enough.
The importance of optimal individualised treatment cannot be emphasized enough. This is because although the leg may be at risk or painful it is actually not the only problem. There is a higher risk of any cardiovascular event (heart attack, stroke etc) for this group of people than the general population.
Critical / Severe Disease
If the blood supply is critically decreased to the lower limb then the nerves also become affected by the lack of oxygen. As humans, we also live by the laws of science and gravity plays a part in our daily living. When we elevate our legs we are removing the force of gravity and this, in effect, decreases the volume of blood to the feet. In healthy subjects, this would not matter and there would still be sufficient blood to the feet and toes.
However, if there is decreased blood supply then decreasing this further by eliminating gravity may be more important. In this instance, there is decreased blood supply to the nerve endings and pain is experienced. This is usually burning in nature and may even awaken one from sleeping. The pain occurs when the legs are elevated, which is usually at night when one goes to bed and lies down. People who experience this often find that by sitting up, and hanging the legs over the edge of the bed, the pain may be relieved to some degree. This severe degree of symptoms is known as Rest Pain.
Lastly the blood supply may be so poor from the stenosis that the tissue cannot survive with so little oxygen and nutrients. In this case arterial ulcers may develop on the feet. If wounds form on the lower legs (for example, from trauma to the foot or ill-fitting shoes) they will not heal within 2 weeks.
In extreme cases gangrene may develop – black, dead tissue. This cannot be reversed but progression needs to be attempted This degree of poor blood flow is known as Tissue Necrosis.
Rest pain and tissue necrosis are classified as critical ischaemia (Ischaemia meaning lack of blood supply) and usually requires dual treatment
- medical management
One needs to remember that surgery will address the immediate problem – that is the leg - however, the disease is not only confined to the leg but also to other organs in the rest of the body. The leg is a marker that the heart and brain are also at risk and medical management aims to reduce this risk.