^T^^B^D: Chronic arterial insufficiency to the lower limbs resulting in consequences ranging from pain on exercise (intermittent claudication) to ulceration or ^^ gangrene.
^^ ^r^A Atherosclerosis in the lower aorta, iliac, femoral or other leg arteries.
Common, prevalence 7-15% of elderly population, male:female is 2:1. Annual incidence of critical limb ischaemia is 50-100/100000 in the UK.
^IH La Fontaine classification system of symptoms: I: Asymptomatic.
II: Intermittent claudication. Crampy pain in the calf, coming on during exercise after a constant distance (claudication distance), relieved within a few minutes of exercise cessation.
III: Rest pain. Severe aching pain that typically comes on in the lower limb at night, with some relief by hanging the leg over side of bed. IV: Limb ulceration or gangrene.
Critical ischaemia: When there is rest pain > 2 weeks, ulceration or gangrene, indicating severe arterial insufficiency threatening the viability of the limb. Leriche's syndrome: When buttock and thigh claudication and impotence result from lower aortic occlusion.
E: Examine the cardiovascular system, looking for signs of hyperlipidaemia, carotid bruits, signs of ischaemic heart disease, abdominal aortic aneurysm. If ischaemia is severe in lower limbs, there is shiny atrophic skin with hair loss or atrophic nails, ulcers tend to be painful and have a 'punched out' appearance (e.g. under toes or classically over lateral malleolus). Peripheries cool to the touch with prolonged capillary return time, weak or absent pulses. Listen for bruits. Buerger's test: Elevation of the leg results in pallor, venous guttering, followed by dependent rubor.
Ankle-brachial pressure index: Measured using a handheld Doppler; determined as the systolic ankle pressure divided by the brachial pressure. Normal > 0.9; claudication 0.8-0.6.
Critical ischaemia < 0.5 or ankle systolic < 50 mmHg or toe systolic < 30 mmHg. (Values may be falsely high in diabetics due to poorly compressible vessels, and absent pulses on palpation replace pressure measurement.)
P: Atherosclerosis causes stenoses in the arterial tree; at rest there must be a > 80% area narrowing before there is a fall in perfusion pressure. During exercise, demand is " and inadequate oxygenation results in relative ischaemia and pain. Critical limb ischaemia is usually due to multisegment disease causing severe ischaemia, such that tissue viability is threatened with risk of ulceration and gangrene.
I: Imaging: Colour duplex may localise disease; however, the gold standard is still angiography, usually digital subtraction angiography as this uses smaller doses of contrast. This should only be performed on those in whom intervention is likely. Use of MRA is increasing (no risk of ionising radiation). Bloods: FBC (for polycythaemia or thrombocythaemia), lipid (for hyperlipidaemia), random glucose (for diabetes).
M: Medical: Stop smoking and exercise, supervised programs have been shown to be effective. Treatment of other cardiovascular risk markers, e.g. statins, control of hypertension (but p-blockers should be avoided as they tend to # peripheral circulation), aspirin. Prostacyclin infusions are sometimes used in those with critical ischaemia unable to tolerate other interventions but this can cause severe hypotension.
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