Patterns of occlusive disease

Legs

Chronic leg ischaemia

Intermittent claudication

In the male general population aged 40-49 years the prevalence of intermittent claudication is approximately 0.5-1%. By 60-69 years this rises approximately four-fold. The prevalence in women is roughly half that in men.

Typically the pain is described as 'cramp like' and felt after walking for a certain distance commencing more rapidly when walking rapidly or uphill. The pain is most often felt in the calf but may develop in the foot, thigh or buttock. It is usually relieved by resting for 2-3 min after which the patient may walk further. This must be differentiated from other causes of intermittent leg pain such as:

• Arthritis: Pain is typically felt as soon as the patient starts to walk, tends to be worse in the mornings and is often partially relieved by exercise. It is often present at rest.

• Neurogenic: Pain usually arises from cauda equina or nerve root compression. It commences after walking a short distance and is only slowly relieved at rest and often only after sitting down. It is commonly associated with back pain or sciatica.

• Venous claudication: There is always a clear history of ileo-femoral venous thrombosis. The pain characteristically is described as 'bursting' and is only slowly relieved by resting with the limb elevated.

Compartment syndrome: This usually affects the anterior compartment of the leg in young athletic individuals and is associated with 'tightness' and swelling of the anterior compartment.

About 75% of patients presenting with claudication will show improvement or maintenance of symptoms. At most only about 10% will ever need amputation or limb salvage procedures. The risk of amputation is increased five-fold in diabetics. However, the mortality from all causes in claudi-cants at 5, 10 and 15 years is approximately 30, 50 and 70%, respectively, which is about twice the rate in the control population. Patients with claudication are therefore up to seven-times more likely to die than to lose a leg.

The aims of treatment are therefore to reduce the rate of deterioration by risk factor management (see above) and exercise to stimulate development of the collateral circulation, possibly as part of a supervised programme.

There is no evidence that vasodilating drugs have any effect on claudicants but metabolically active drugs such as naftidrofuryl or viscosity-reducing drugs like oxpentifylline may have a marginal effect.

Disease causing isolated calf symptoms is often limited to the superficial femoral or popliteal artery and balloon angioplasty of these lesions tends to be technically feasible. However there is no level one evidence that angioplasty is superior to conservative management. Supra-inguinal disease often causes thigh and/or buttock symptoms and may have a poorer response to conservative management. It would seem sensible to offer balloon angioplasty, with a complication risk of 1-4%, to patients with short lesions (<10 cm) not responding to a trial of conservative management.

Critical ischaemia

This is defined as rest pain most nights in spite of adequate analgesia, tissue loss or an ankle Doppler pressure <50 mmHg. Rest pain is an unremitting pain felt in the toes or the forefoot. It tends to be worse in bed and may be partially relieved by hanging it out of the bed or walking round. It is a particularly debilitating form of pain. Pain felt only in the leg or thigh at night is not ischaemic rest pain. Tissue loss in this context implies gangrene or ulceration of the non-diabetic foot with an ABPI < 0.5.

Critical ischaemia usually requires intervention, often a combination of open surgery and endovascular procedures, to salvage the leg or primary amputation.

Re-vascularisation of the leg requires that three factors be addressed:

1. Inflow: Haemodynamically significant stenoses (>50%) or occlusions in the aorto-iliac segment must be treated, either by angioplasty ± stenting of short iliac lesions or aorto-bi-femoral, axillo-bi-femoral or femero-femoral cross-over grafting if the lesion is too long. If the common femoral and profunda femoris arteries are patent this will usually be sufficient to salvage a leg with rest pain but more distal reconstruction is usually required if there is tissue loss. Endarterectomy may be used for localised stenoses or occlusions of the aorta, common iliac or common femoral arteries.

2. Conduit: For long occlusions of the femero-popliteal and crural vessels the preferred conduit is long saphenous vein (Fig. 15.12). If this is not available and vein cannot be harvested from the contra-lateral leg or arms then a prosthetic

Figure 15.12. Reversed vein arterial bypass surgery.

graft may be necessary. A cuff of vein interposed between the prosthesis and the artery at the distal anastomosis improves patency. Subintimal angioplasty is a technique whereby balloon angioplasty is deliberately performed in the space between the intima and media, rather than the lumen of the artery. Much longer lesions (>10 cm) can now be treated in this way. There is much debate regarding the relative long-term patency of infra-inguinal bypass grafts or subintimal angioplasty and clinical trials are underway. As long as the conduit remains patent for sufficient time to allow healing of distal tissue loss and a collateral circulation to develop then limb salvage is usually achieved if the inflow and profunda vessels remain open.

3. Run-off: There must be a patent crural vessel in continuity with the arch vessels of the foot. This is necessary either for a bypass graft to be anastomosed onto or for a subintimal angioplasty tract to re-enter an arterial lumen. Any re-vascularisation procedure will fail if this condition is not met.

Acute leg ischaemia

An acutely ischaemic leg is either due to an embolus lodging in a previously healthy artery (Fig. 15.13) or thrombosis in an artery which virtually always has underlying disease or has been damaged by a traumatic event. The occlusion has been too sudden for an effective collateral system to develop and this is a surgical emergency. The diagnosis and management of an acutely ischaemic leg is challenging but can be extremely rewarding.

The history is of sudden onset coldness, weakness, pain and numbness of the affected limb. On examination pulses are absent and diagnosis is obvious if the foot is white. However the foot may appear pink, especially if dependant, by the time the patient arrives in hospital. Clues to the urgency of the situation are neuromuscular deficit and/or tender muscle compartments. The former may be quite a subtle altered sensation and weakness of extension of the great toe compared to the other side, the latter signifies

Figure 15.13. Brachial embolectomy.

Figure 15.12. Reversed vein arterial bypass surgery.

Figure 15.13. Brachial embolectomy.

severe muscular ischaemia which will progress to muscle death over a few hours. Extensive fixed mottling of the skin suggests that the limb is unsalvageable.

An embolus should be strongly suspected if there is no previous history suggestive of peripheral vascular disease, no signs of chronic ischaemia (hair loss, nail disruption, muscle wasting), palpable pulses in the other foot and the patient is in atrial fibrillation. If all the above conditions are met an embolectomy under local anaesthetic can be limb and life saving in even the most elderly patients.

Acute intra-arterial thrombosis may occur in a tightly stenosed atherosclerotic vessel, a stenosed bypass graft, a peripheral aneurysm or following trauma (blunt, penetrating or iatrogenic). Rarely intra-arterial thrombosis may occur in previously healthy vessels when there is a severe systemic illness (e.g. malignancy, HIV, anti-phospholipid syndrome). Stasis and thrombosis in diseased vessels may be induced by dehydration, immobility, low cardiac output or polycythaemia. The mortality associated with acute ischaemia remains high as thrombosis or embolism is not infrequently a pre-terminal event in patients dying from other causes such as cardiac failure. In these cases aggressive treatment may be contraindicated.

Management of the acutely ischaemic leg involves:

• if irreversibly ischaemic, amputate when demarcated;

• immediately heparinise (may double limb-salvage rate);

• after successful embolectomy, anticoagulate, if not con-traindicated, to prevent recurrence;

• if thrombotic, investigate acutely with a view to immediate limb salvage surgery as above;

• following successful re-vascularisation, the limb must be checked for evidence of compartment syndrome and fasciotomy should be performed if in any doubt.

Intra-arterial thrombolysis: (Fig. 15.14)

This technique is now less commonly used in the acutely ischaemic leg for the following reasons:

• it was expensive, not always successful, had a high re-occlusion rate and carried a significant morbidity especially in the elderly (haemorrhage, haemorrhagic stroke and distal embolisation);

• there was usually an underlying problem that required surgery anyway;

• if neuromuscular deficit was present the technique could be too slow to prevent permanent tissue damage.

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