ABC of Vascular Disease

Occlusive Arterial Disease

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1. What is occlusive arterial disease?
Occlusive arterial disease (OAD) is a slow process through which arteries throughout the body become progressively narrowed and eventually completely blocked.

bulletOcclusive arterial disease is very common and will affect every person to some degree.
bulletOcclusive arterial disease develops slowly throughout life.
bulletOcclusive arterial disease affects all the arteries in the body to some degree.
bulletOcclusive arterial disease causes life threatening complications when it affects the the arteries to the vital organs (e.g. heart, brain, kidneys, etc).
bulletOcclusive arterial disease is the commonest cause of death in Western countries.

2. What causes occlusive arterial disease?
The arteries are not simply rubbery tubes that carry blood from the heart; they are complex, living structures.  The most delicate part of an artery is the lining which is called the endothelium. The endothelium is only one cell thick and is like a very thin and delicate skin on the inside of the arteries.  The endothelium is so thin that it can only just be seen even with a microscope.  The endothelium is very important because it seals the inside of the artery and also prevents the blood from sticking to the inside of the artery and forming blood clots.  If the endothelium is damaged it becomes leaky and if the endothelium is lost completely the wall of the artery is exposed to the blood and a blood clot will develop inside the artery.  Rather like the skin on the surface of the body, the endothelium can heal if it is damaged.  However. if the endothelium is damaged over and over again a type of scar develops which forms a bump on the inside of the artery.  There are many things that can damage the endothelium; toxic molecules in the blood and physical damage are the two most common.  For example, burning a cigarette generates dozens of chemical products in the smoke that, when inhaled into the lungs, are absorbed into the blood and distributed by the blood all around the body.  The arterial endothelium is damaged by some of these chemicals and becomes slightly "leaky".  This allows other molecules in the blood, such as cholesterol, to leak into the wall of the artery and cause problems by irritating the cells in the wall of the artery.  If this type of damage is repeated over and over the wall of the artery is becomes progressively more and more scarred and a large bump grows into the inside of the artery.  This bump is called atheroma, which literally means "lump of porridge" because that is a bit what it looks like when it is removed!  The atheroma gradually narrows the artery and progressively reduces the flow of blood.  More seriously, the atheroma can suddenly give way and block the artery, completely and irreversibly.  If this sudden event happens in one of the arteries that supply blood to the heart muscle it is called a heart attack.  If it is the one of the main arteries to the heart, the heart muscle will fail, the heart will not pump and the person will not survive.

3. Is smoking the only cause of occlusive arterial disease?
No, anything that causes damage to the delicate endothelial lining of the arteries over a long period of time will result in irreversible occlusive arterial disease.  In many people there is a combination of factors at work and the more factors that are active the greater the risk of developing arterial disease.  The major risk factors for arterial disease are:

bulletAge
bulletSmoking
bulletMale gender
bulletHigh blood fat (hyperlipidaemia)
bulletHigh blood pressure (hypertension)
bulletSugar diabetes (diabetes mellitus)
bulletUnfavourable genes

If and when a person will develop symptoms of arterial disease cannot be predicted, but the more risk factors that are present the greater the chance.  It's a bit like driving: if you drive fast with your eyes closed you are more likely to have an accident than if you drive slowly with your eyes open; but you cannot predict if an accident will happen, when it will happen and how bad it will be.  The safest strategy is to reduce the risks as much as possible then keep your fingers crossed.  With arterial disease, some of the risk factors cannot be altered (age, gender and genes for example) but other factors can be eliminated (smoking) or at least controlled (high blood pressure, high blood fat, diabetes).

4. If I stop smoking will the arterial disease go away?
Unfortunately not, but the symptoms caused by arterial disease often improve considerably and the rate of progression arterial disease will be reduced.  There are other good health reasons to stop smoking: it is the single most important cause of lung cancer and other serious diseases of the lungs. 

5. What will happen if I have occlusive arterial disease and do nothing about it?
Occlusive arterial disease is a progressive systemic condition.  This means that it gets worse with time and will eventually affect all parts of the systemic arterial circulation.  The most common complication is the result of disease affecting the arteries to the heart itself and results in fatal heart attack, chest pain, heart failure, irregular heart rhythms, loss of mobility, loss of independence and poor quality of life.  Blocked arteries to the legs results in pain on exercise (intermittent claudication) which may progress to constant, severe pain in the feet, leg ulcers and gangrene (critical limb ischaemia).  Diseased arteries in the neck and head can result in a fatal stroke or permanent brain damage with severe mental and physical disabilities.  Damage to the arteries to the kidneys can result in dangerously high blood pressure and renal failure.

6. What can I do to prevent occlusive arterial disease getting worse?
The simple answer is stop doing the things that are making it worse (i.e. smoking), and seek medical advice regarding testing for the other treatable risk factors and getting treatment if they are confirmed.  Patients with high blood pressure, high blood fat and diabetes can be treated very effectively using modern drugs.

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S.R.Dodds 2001

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