Peripheral Arterial Disease

Peripheral arterial disease (PAD) refers to the narrowing of the arteries supplying the limbs and periphery, reducing the blood supply to these areas. It usually refers to the lower limbs, resulting in symptoms of claudication.

Intermittent claudication is a symptom of ischaemia in a limb, occurring during exertion and relieved by rest. It is typically a crampy, achy pain in the calf, thigh or buttock muscles associated with muscle fatigue when walking beyond a certain intensity.

Critical limb ischaemia is the end-stage of peripheral arterial disease, where there is an inadequate supply of blood to a limb to allow it to function normally at rest. The features are pain at rest, non-healing ulcers and gangrene. There is a significant risk of losing the limb.

Acute limb ischaemia refers to a rapid onset of ischaemia in a limb. Typically, this is due to a thrombus (clot) blocking the arterial supply of a distal limb, similar to a thrombus blocking a coronary artery in myocardial infarction.

Ischaemia refers to an inadequate oxygen supply to the tissues due to reduced blood supply.

Necrosis refers to the death of tissue.

Gangrene refers to the death of the tissue, specifically due to an inadequate blood supply.

 

Atherosclerosis

Athero- refers to soft or porridge-like and -sclerosis refers to hardening. Atherosclerosis is a combination of atheromas (fatty deposits in the artery walls) and sclerosis (the process of hardening or stiffening of the blood vessel walls). Atherosclerosis affects the medium and large arteries. It is caused by chronic inflammation and activation of the immune system in the artery wall. Lipids are deposited in the artery wall, followed by the development of fibrous atheromatous plaques.

 

These plaques cause:

  • Stiffening of the artery walls, leading to hypertension (raised blood pressure) and strain on the heart (whilst trying to pump blood against increased resistance)
  • Stenosis, leading to reduced blood flow (e.g., in angina)
  • Plaque rupture, resulting in a thrombus that can block a distal vessel and cause ischaemia (e.g., in acute coronary syndrome)

 

Atherosclerosis Risk Factors

It is important to break these down into modifiable and non-modifiable risk factors. We can do nothing about non-modifiable risk factors, but we can do something about modifiable ones.

 

Non-modifiable risk factors:

  • Older age
  • Family history
  • Male

 

Modifiable risk factors:

  • Smoking
  • Alcohol consumption
  • Poor diet (high in sugar and trans-fat and low in fruit, vegetables and omega 3s)
  • Low exercise / sedentary lifestyle
  • Obesity
  • Poor sleep
  • Stress

 

Medical Co-Morbidities

Medical co-morbidities increase the risk of atherosclerosis and should be carefully managed to minimise the risk:

  • Diabetes
  • Hypertension
  • Chronic kidney disease
  • Inflammatory conditions such as rheumatoid arthritis
  • Atypical antipsychotic medications

 

TOM TIP: Think about risk factors when taking a history from someone with suspected atherosclerotic disease (such as someone presenting with intermittent claudication). Ask about their exercise, diet, past medical history, family history, occupation, smoking, alcohol intake and medications. This will help you perform well in exams and when presenting to seniors.

 

End Results of Atherosclerosis

  • Angina
  • Myocardial infarction
  • Transient ischaemic attack
  • Stroke
  • Peripheral arterial disease
  • Chronic mesenteric ischaemia

 

Intermittent Claudication

Peripheral arterial disease presents with intermittent claudication. Patients describe a crampy pain that predictably occurs after walking a certain distance. After stopping and resting, the pain will disappear. The most common location is the calf muscles, but it can also affect the thighs and buttocks.

 

Critical Limb Ischaemia

The features of critical limb ischaemia can be remembered with the “6 P’s” mnemonic:

  • Pain
  • Pallor
  • Pulseless
  • Paralysis
  • Paraesthesia (abnormal sensation or “pins and needles”)
  • Perishing cold

 

Critical limb ischaemia typically causes burning pain. It is worse at night when the leg is raised, as gravity no longer helps pull blood into the foot.

 

Leriche Syndrome

Leriche syndrome occurs with occlusion in the distal aorta or proximal common iliac artery. There is a clinical triad of:

  • Thigh/buttock claudication
  • Absent femoral pulses
  • Male impotence

 

Signs on Examination

Look for risk factors:

  • Tar staining on the fingers
  • Xanthomata (yellow cholesterol deposits on the skin)

 

Looks for signs of cardiovascular disease:

  • Missing limbs or digits after previous amputations
  • Midline sternotomy scar (previous CABG)
  • A scar on the inner calf for saphenous vein harvesting (previous CABG)
  • Focal weakness suggestive of a previous stroke

 

The peripheral pulses may be weak on palpation:

  • Radial
  • Brachial
  • Carotid
  • Abdominal aorta
  • Femoral
  • Popliteal
  • Posterior tibial
  • Dorsalis pedis

 

You can use a hand-held Doppler to accurately assess the pulses when they are difficult to palpate.

 

Signs of arterial disease on inspection are:

  • Skin pallor
  • Cyanosis
  • Dependent rubor (a deep red colour when the limb is lower than the rest of the body)
  • Muscle wasting
  • Hair loss
  • Ulcers
  • Poor wound healing
  • Gangrene (breakdown of skin and a dark red/black change in colouration)

 

On examination, there may be:

  • Reduced skin temperature
  • Reduce sensation
  • Prolonged capillary refill time (more than 2 seconds)
  • Changes during Buerger’s test

 

Buerger’s Test

Buerger’s test is used to assess for peripheral arterial disease in the leg. There are two parts to the test.

The first part involves the patient lying on their back (supine). Lift the patient’s legs to an angle of 45 degrees at the hip. Hold them there for 1-2 minutes, looking for pallor. Pallor indicates the arterial supply is not adequate to overcome gravity, suggesting peripheral arterial disease. Buerger’s angle refers to the angle at which the leg is pale due to inadequate blood supply. For example, a Buerger’s angle of 30 degrees means that the legs go pale when lifted to 30 degrees.

The second part involves sitting the patient up with their legs hanging over the side of the bed. Blood will flow back into the legs assisted by gravity. In a healthy patient, the legs will remain a normal pink colour. In a patient with peripheral arterial disease, they will go:

  • Blue initially, as the ischaemic tissue deoxygenates the blood
  • Dark red after a short time, due to vasodilation in response to the waste products of anaerobic respiration

 

The dark red colour is referred to as rubor.

 

Leg Ulcers

Leg ulcers indicate the skin and tissues are struggling to heal due to impaired blood flow. Some features help you distinguish between arterial and venous ulcers.

Arterial ulcers are caused by ischaemia secondary to an inadequate blood supply. Typically, arterial ulcers:

  • Are smaller than venous ulcers
  • Are deeper than venous ulcers
  • Have well defined borders
  • Have a “punched-out” appearance
  • Occur peripherally (e.g., on the toes)
  • Have reduced bleeding
  • Are painful

 

Venous ulcers are caused by impaired drainage and pooling of blood in the legs. Typically, venous ulcers:

  • Occur after a minor injury to the leg
  • Are larger than arterial ulcers
  • Are more superficial than arterial ulcers
  • Have irregular, gently sloping borders
  • Affect the gaiter area of the leg (from the mid-calf down to the ankle)
  • Are less painful than arterial ulcers
  • Occur with other signs of chronic venous insufficiency (e.g., haemosiderin staining and venous eczema)

 

Investigations

  • Ankle-brachial pressure index (ABPI)
  • Duplex ultrasound – ultrasound that shows the speed and volume of blood flow
  • Angiography (CT or MRI) – using contrast to highlight the arterial circulation

 

Ankle-Brachial Pressure Index

Ankle-brachial pressure index (ABPI) is the ratio of systolic blood pressure (SBP) in the ankle (around the lower calf) compared with the systolic blood pressure in the arm. These readings are taken manually using a Doppler probe. For example, an ankle SBP of 80 and an arm SBP of 100 gives a ratio of 0.8 (80/100).

Results:

  • 0.9 – 1.3 is normal
  • 0.6 – 0.9 indicates mild peripheral arterial disease
  • 0.3 – 0.6 indicates moderate to severe peripheral arterial disease
  • Less than 0.3 indicates severe disease to critical ischaemic

 

An ABPI above 1.3 can indicate calcification of the arteries, making them difficult to compress. This is more common in diabetic patients.

 

Management of Intermittent Claudication

Lifestyle changes are required to manage modifiable risk factors (e.g., stop smoking). Optimise medical treatment of co-morbidities (such as hypertension and diabetes).

 

Exercise training, involving a structured and supervised program of regularly walking to the point of near-maximal claudication and pain, then resting and repeating.

 

Medical treatments:

  • Atorvastatin 80mg
  • Clopidogrel 75mg once daily (aspirin if clopidogrel is unsuitable)
  • Naftidrofuryl oxalate (5-HT2 receptor antagonist that acts as a peripheral vasodilator)

 

Surgical options:

  • Endovascular angioplasty and stenting
  • Endarterectomy – cutting the vessel open and removing the atheromatous plaque
  • Bypass surgery – using a graft to bypass the blockage

 

Endovascular angioplasty and stenting involve inserting a catheter through the arterial system under x-ray guidance. At the site of the stenosis, a balloon is inflated to create space in the lumen. A stent is inserted to keep the artery open. Endovascular treatments have lower risks but might not be suitable for more extensive disease.

 

Management of Critical Limb Ischaemia

Patients with critical limb ischaemia require urgent referral to the vascular team. They require analgesia to manage the pain.

Urgent revascularisation can be achieved by:

  • Endovascular angioplasty and stenting
  • Endarterectomy
  • Bypass surgery
  • Amputation of the limb if it is not possible to restore the blood supply

 

Management of Acute Limb Ischaemia

Patients with acute limb ischaemia need an urgent referral to the on-call vascular team for assessment.

Management options include:

  • Endovascular thrombolysis – inserting a catheter through the arterial system to apply thrombolysis directly into the clot
  • Endovascular thrombectomy – inserting a catheter through the arterial system and removing the thrombus by aspiration or mechanical devices
  • Surgical thrombectomy – cutting open the vessel and removing the thrombus
  • Endarterectomy
  • Bypass surgery
  • Amputation of the limb if it is not possible to restore the blood supply

 

Last updated May 2021
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