Chronic Limb Ischaemia

Chronic limb ischaemia is peripheral arterial disease that results in a symptomatic reduced blood supply to the limbs. It is typically caused by atherosclerosis (rarely vasculitis) and will commonly affect the lower limbs (however the upper limbs and pelvis can also be affected).

In this article, we shall look at the clinical features, investigations and management of chronic limb ischaemia.


Risk Factors

  • Smoking
  • Diabetes mellitus
  • Hypertension
  • Hyperlipidaemia
  • Age
  • Family history
  • Obesity and physical inactivity

Around 15-20% individuals over 70yrs have peripheral arterial disease. The Framingham study (Circulation 1997) demonstrated an increase in the prevalence of the disease from 0.4 per 1000 males aged 35-45yrs to 6 per 1000 males aged older than 65yrs.


Clinical Features

The clinical features of chronic limb ischaemia depend on its severity (Table 1). One of the earlier symptoms is intermittent claudication – a cramping-type pain in the calf, thigh, or buttock after walking a fixed distance (the ‘claudication distance’), relieved immediately by rest within minutes.

Stage I Asymptomatic
Stage II Intermittent claudication
Stage III Ischaemic rest pain
Stage IV Ulceration or gangrene, or both

Table 1: Fontaine classification of chronic leg ischaemia

Leriche Syndrome

Leriche syndrome is a form of peripheral arterial disease affecting the aortic bifurcation. It specifically presents with buttock or thigh pain, and associated erectile dysfunction.

Critical Limb Ischaemia

Critical limb ischaemia is the advanced form of chronic limb ischaemia. It can be clinically defined in three ways:

Fig 1 - Gangrene as a result of peripheral vascular disease, indicating critical limb ischaemia.

Fig 1 – Gangrene as a result of peripheral vascular disease, indicating critical limb ischaemia.

  • Ischaemic rest pain for greater than 2 weeks duration, requiring opiate analgesia
  • Presence of ischaemic lesions / gangrene objectively attributable to the arterial occlusive disease
  • ABPI less than 0.5

On examination, the limbs may be pale and cold, with weak or absent pulses. Other signs include limb hair loss, skin changes (atrophic skin, ulceration, or gangrene) and thickened nails.

Buerger’s test

Buerger’s test involves lying the patient supine and raising their legs until they go pale and then lowering them until the colour returns (or even becoming hyperaemic). The angle at which limb colour returns is termed Buerger’s angle; an angle of less than 20 degrees indicates severe ischaemia.


Differential Diagnoses

There are two major differential diagnoses for a patient presenting with limb ischaemia symptoms:

  • Spinal stenosis (‘neurogenic claudication’)
    • Typically have pain from the back radiating down the lateral aspect of the leg (tensor fascia lata)
    • Often have symptoms on initial movement, or symptoms that are relieved by sitting rather than standing.
  • Acute limb ischaemia
    • By definition, is less than 14 days duration and patients often present within hours.

Acute on Chronic ischaemia is more complex condition whereby there is an acute often embolic event in a patient with previous peripheral arterial disease. These patients are sub-classified as they typically have a longer duration in which the limb is salvageable.


Investigations

The diagnosis of chronic limb ischaemia is clinical. The ankle-brachial pressure index (ABPI) is used to confirm the diagnosis and quantify severity of chronic limb ischaemia:

Normal >0.9
Mild 0.8-0.9
Moderate 0.5-0.8
Severe <0.5
Fig 2 - The ankle-brachial pressure index (ABPI). A value of less than 0.9 indicates a reduce blood supply to the lower limbs.

Fig 2 – The ankle-brachial pressure index (ABPI). A value of less than 0.9 indicates a reduce blood supply to the lower limbs.

Any ABPI value >1.2 should be interpreted with caution, as calcification and hardening of the arteries may cause a falsely high ABPI.

Any critical limb ischaemia should be investigated initially with a Doppler ultrasound, used to assess the severity and anatomical location of any occlusion. Further imaging can be achieved via CT angiography or magnetic resonance angiogram (MRA).

Due to concurrent cardiovascular risk factors seen in patients with chronic limb ischaemia, patients should also have a cardiovascular risk assessment. This includes blood pressure, blood glucose, lipid profile and ECG. In addition, any patient presenting with chronic limb ischaemia <50yrs without significant risk factors should also have a thrombophilia screen and homocysteine levels checked.


Management

Medical Management

Most patients with chronic limb ischaemia require cardiovascular risk factor modification:

  • Lifestyle advice (smoking cessation, regular exercise, weight reduction)
  • Statin therapy
  • Aspirin or clopidogrel
  • Optimise diabetes control

The course of chronic limb ischaemia is variable and many patients’ symptoms do improve on lifestyle changes and medical management alone.

Surgical Management

Fig 3 - Angioplasty and stenting. This is one of the surgical options available for the treatment of chronic limb ischaemia.

Fig 3 – Angioplasty and stenting. This is one of the surgical options available for the treatment of chronic limb ischaemia.

NICE guidance states that surgical intervention can be offered in suitable patients if (i) risk factor modification has been discussed; and (ii) supervised exercise has failed to improve symptoms. Any patients with critical limb ischaemia should be urgently referred for surgical intervention.

There are two main surgical options available:

  • Angioplasty with stenting, typically for treating single occluded regions
  • Bypass grafting, typically used for diffuse disease

Amputations are considered for any patients who are unsuitable for revascularisation with ischaemia causing incurable symptoms or gangrene leading to sepsis.


Complications

  • Reduced mobility and quality of life
  • Amputation
  • Acute-on chronic limb ischaemia
  • Sepsis, secondary to infected gangrene

Over a 5 year period, of those patients with intermittent claudication:

  • Most will have stable claudication
  • 10-20% develop worsening symptoms
  • 5-10% develop critical limb ischaemia
  • Amputation is eventually required in 1-2% (increases to 5% in people with diabetes)

Two years following a below-knee amputation for chronic limb ischaemia, 15% require a further above knee amputation, 30% have died, and only 40% have full mobility.

The 5 -year mortality rate in those diagnosed with chronic limb ischaemia is around 50%.

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