Chronic limb ischaemia

Notes

Overview

Chronic limb ischaemia refers to the development of reduced perfusion to the lower limbs.

Peripheral artery disease (PAD) is characterised by the presence of narrowing’s or occlusion of peripheral arteries leading to compromise of blood supply to the lower limbs.

As with many areas of medicine terminology can be confusing. In this note we follow terminology referred to in the 2017 ESC guidance on peripheral arterial diseases. Peripheral arterial diseases refers to ‘all arterial disease other than coronary arteries and the aorta’. Peripheral artery disease refers to what may also be termed lower extremity artery disease (LEAD). 

It can be categorised as acute or chronic depending on the presentation:

  • Acute limb ischaemia: refers to a sudden decrease in blood supply resulting in ischaemic injury. Typically the features are said to develop in less than 2 weeks.
  • Chronic limb ischaemia: refers to chronic narrowing of peripheral arteries resulting in intermittent claudication, rest pain and may threaten limb viability. 

Risk factors

Smoking and diabetes are the two most significant risk factors for developing PAD.

  • Smoking
  • Diabetes
  • Age
  • Hypertension
  • Hyperlipidaemia
  • Obesity
  • Raised homocysteine

It appears patients of black ethnicity have greater risk of chronic limb ischaemia, though this may be in part due to higher incidence of factors described above. Of note, in western countries, those of black ethnicity are at greater risk of complications and amputation (see here for more details). Further research is needed to understand and combat these racial disparities.

Clinical features

Early LEAD is typically asymptomatic, with intermittent claudication commonly the first symptom experienced.

Intermittent claudication

Cramp-like muscular pain in the lower limbs (typically affecting the calves). Symptoms are triggered by exercise / walking and relieved by rest.

Foot pulses may be absent and there is increased risk of non-healing skin injuries. Hair loss in the lower limbs may be evident. Erectile dysfunction is common.

Critical / limb threatening ischaemia

Rest pain, pain experienced at rest, heralds the development of critical / limb threatening ischaemia. Pain is often worse at night due to reduced action of gravitational forces, characteristically the patient hangs a leg of the edge of the bed to relieve symptoms.

Foot pulses are often absent. Ulcers, infections, gangrene and tissue loss may all occur.

Investigations

An ankle-brachial index is the first-line investigation in those with suspected lower extremity artery disease.

Ankle-brachial index

An ankle-brachial index (ABI) is typically the first-line investigation. It compares the blood pressure at the ankle and the arm. The ABI is calculated by dividing the ankle systolic BP by the arm systolic BP.

A low ABI (< 0.9) is indicative of lower extremity artery disease. It is not a perfect test, those with borderline results, or in whom suspicion persists further tests are required.

High ABI (> 1.40) is indicative of vessel wall calcification. Alternative tests like doppler US and toe brachial index (TBI) may be used.

Ankle brachial pressure index categories

Treadmill test

Treadmill is used to identify those with peripheral artery disease. Strandness protocol involves walking at 3 km/h on a 10% slope.

The test can be continued until the patient needs to stop due to pain. A decrease in ankle systolic BP of > 30 mmHg or ABI decrease > 20% is diagnostic of lower extremity artery disease.

Imaging

Duplex US: May be combined with ABI and exercise tests to diagnose lower extremity artery disease.

CT angiography: Offers good views of vessels, as well as identifying aneurysms and previous interventions. Involves radiation and contrast (consider renal function and sensitivity).

MR angiography: Offers good views of vessels and may be useful in identifying stenosis in calcified vessels. No radiation, but costly and time consuming. Metal stents / prosthesis may distort images.

Interventional

Digital subtraction angiography: An invasive technique that utilises catheter guided contrast injection combined with fluoroscopy and digital subtraction to isolate the vessels.

Rutherford classification

The Rutherford classification can be used to grade chronic limb ischaemia.

Rutherford classification of chronic limb ischaemia

Medical therapy

Medical treatments are aimed at improving symptoms, reducing progression and addressing general cardiovascular risk factors.

All patients should be evaluated for hypertension and diabetes and treated accordingly.

Modifiable risk factors

It is key patients understand their condition and how modifiable risk factors can impact its progression. Smoking cessation is of the utmost importance. 

Regular exercise should be encouraged. Plans should take into account individuals abilities and co-morbidities. Dietary advice and appropriate weight loss should be supported.

Pharmacological

  • Lipid therapy: Statins should typically be offered.
  • Anti-platelet therapy: All patients with peripheral arterial disease should be offered Aspirin or Clopidogrel as secondary prevention.
  • Naftidrofuryl oxalate: Is a peripheral vasodilators that may be considered in patients in whom conservative measures have failed and decline surgical options.

Revascularisation

Revascularisation techniques can be categorised as surgical or endovascular.

Revascularisation should be considered in patients with intermittent claudication who have failed conservative measures. All patients with critical limb ischaemia (where appropriate) should be urgently referred for review and discussion at the vascular MDT. 

Choice of intervention is complex and nuanced. It is based upon the pattern of disease and patient based factors. Here we outline some of the options that may be considered.

Endovascular

Angioplasty +/- stent: Balloon angioplasty involves the opening up of areas of stenosis often followed by stent deployment.

Remote endarterectomy: Considered a hybrid procedure, involves the removal of plaque from within a vessel, often combined with stent.

Surgical

Bypass: Vessel (synthetic or autologous) is used to bypass the diseased segment of artery.

Prognosis

The majority of those with intermittent claudication will develop stable disease.

In those with intermittent claudication around 5-10% will develop critical limb ischaemia and 1-2% will require amputation. Diabetes is associated with a significantly increased risk of amputation to around 5%.

Cardiovascular disease is rarely isolated to the peripheries and so risk of stroke and MI are increased. Patients with peripheral arterial disease are 3 times as likely to die from cardiovascular diseases.

For more facts and figures see NICE CKS.

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