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The word ischaemia is derived from the Greek "ischo" to keep back and "haima" blood. Ischaemia is caused by diseases that lead to arterial narrowing or occlusion. It can vary in severity from very mild and only detectable by the surgeon to very severe and potentially limb threatening. Arteries of the lower limbs are particularly vulnerable to atherosclerotic occlusive disease. When one or more of the main arteries to the leg become narrowed by 50% or more, blood flow to the leg is reduced enough to produce symptoms. The most common symptom of leg arterial disease is "claudication" or pain on walking. This condition affects approximately 5% of the adult population, men being twice as likely to be affected. Typically, claudication starts as a cramp like pain in a large group of muscles such as the calf, thigh or buttock. This gripping pain occurs after walking for a distance that varies according to the severity of the disease. This so called "claudication distance" is a very useful -all be it crude- method of judging the severity of ischaemia. Once the affected limb is rested by sitting or stopping walking, the pain disappears promptly. In its severest form, claudication pain can occur after walking for only few metres. In advanced conditions of occlusive arterial disease, blood supply to the leg can be severely compromised to the extent that very little actually reaches the foot. This severe shortage of blood or "critical ischaemia" can manifest itself in the form of rest pain, tissue loss or both. The incidence of critical limb ischaemia is in the range of 1:1,500 adult population. Rest pain typically affects the feet upon lying flat. It is usually quite sharp, severe and constant. Patients find sleeping in a chair or having short walks around the bed useful in easing rest pain. This is because in these positions, gravity helps to draw slightly more blood to the feet. Rest pain can be difficult to control with ordinary analgesics and is one of the symptoms that prompts the surgeon to take urgent action to improve the circulation. The other manifestation of critical ischaemia is tissue loss. This can be in the form of non-healing ulceration or death of the skin or the whole of a digit (ischaemic necrosis). Although the majority of leg ulcers are not caused by ischaemia, it is important to exclude it as a cause. Ischaemic ulcers typically follow minor injury. The ulcers then fail to heal and may gradually enlarge. With critical ischaemia, blood flow to parts at the very end of the leg such as toes or the forefoot may not be sufficient to keep them alive. These parts then undergo a series of colour changes and eventually die. Depending on the rapidity of this death, the parts affected may become painful and infected or dry and mummified. There could be rapid spread of these changes to affect surrounding areas and eventually the whole leg or the changes can be very limited and localised. As the only treatment of critical ischaemia is restoration of blood flow, patients with such a condition are usually admitted to hospital urgently. After undergoing various investigations, the surgeon decides on the most suitable procedure to restore the blood flow to the leg. |
This patient has developed an area of skin ischaemic necrosis (death) due to severe shortage of blood.
This is an angiogram (x ray of the arteries) of both legs. The right main artery to the leg is occluded. A large "collateral" vessel has developed as a result. The left leg shows a bypass graft for a similar problem. |
