Topic 6- lower extremity arterial disease

Question 1

Define limb ischaemia

Answer 1

Vascular disease causes limb ischaemia due to loss of blood pressure via a number of pathologies. Pathologies usually relate to stenosis, occlusion or aneurysm. The degree of narrowing and pressure loss makes the distribution of symptoms and the severity variable

Question 2

What is the most common cause of lower limb ischaemia?

Answer 2

Atherosclerosis

Question 3

List some features of ischaemia

Answer 3

• Presence of pedal pulses from PTA and DPA
• Femoral pulse
• Trophic changes in the feet such as thickened toe nails, dry hairless skin, gangrene and cyanosis
• history of claudication

Question 4

What is claudication?

Answer 4

Claudication is pain experienced during exercise due to loss of blood pressure. Intermittent claudication is ischaemic pain during exercise which is relieved once the patient stops exercising. It is described as cramping, tiredness, tightness, aching and pain. Thigh and buttock claudication can indicate proximal artery disease

Question 5

What is the cause of claudication?

Answer 5

It is usually associated with atherosclerosis but can be caused by spinal canal stenosis, adventitial cysts and entrapment syndrome

Question 6

What is critical limb ischaemia?

Answer 6

Critical limb ischaemia is when the level of ischaemia causes tissue loss in the extremity. It is associated with extensive ischaemic changes and often with severe claudication and rest pain.

Question 7

What is rest pain?

Answer 7

Rest pain is ischaemic pain when there is insufficient pressure to adequately supply the leg at rest. Rest pain usually occurs in the toes and foot, but can be experienced in the ankle.

Question 8

What are features of rest pain?

Answer 8

Features are pain while supine that is relieved by hanging the leg over the bed

Question 9

Why does hanging the leg over the bed relieve rest pain?

Answer 9

This is thought to be due to the increase in hydrostatic pressure which is enough to provide sufficient pressure to re-perfuse the tissue.

Question 10

Where do lower limb aneurysms occur?

Answer 10

Common femoral and popliteal.

Question 11

What is a false aneurysm? `

Answer 11

A false aneurysm is a pseudoaneurysm that is a collection of arterial blood which leaks from an artery and is constrained by the adventitia and fibrous tissue adjacent to its source artery. Often results from leakage from a needle puncture which does not heal. False aneurysms can rupture, thrombose the feeding artery or embolize mural thrombus to occlude distal arteries.

Question 12

What are the 6 features of acute ischaemia?

Answer 12

Pulselessness
Pallor
Paresthesia
Paralysis
Poikilothermia
Pain

Question 13

What causes acute occlusion of an artery?

Answer 13

• embolisation from a proximal source

- thrombosis of an atherosclerotic artery or bypass graft

Question 14

What is arterial thrombosis?

Answer 14

Sudden formation of thrombus can be associated with an ulcerated or ruptured plaque. Graft may form a thrombus associated with a stenosis or from residual valve or fibrous bands. Not all occlusive thrombus produce symptoms of acute occlusion

Question 15

What is Klippel-Trenaunay syndrome?

Answer 15

It is a capillary and venous malformation. It can cause limb swelling and varicose veins. The malformations do not disturb the blood flow to the leg. Patients usually have a good prognosis.

Question 16

What is Parkes Webber syndrome?

Answer 16

Parkes Webber syndrome is a capillary malformation with arterial malformations. Patients may develop varicose veins. Arterial involvement is usually associated with greater morbidity from increased leg length, ulceration and pain. The heart can enlarge due to increased cardiac output associated with degree of malformation present.

Question 17

How do AV-fistulae form?

Answer 17

Formation mostly occurs due to trauma or related pathology such as erosion of an aneurysm, neoplasm or abscess

Question 18

How do traumatic AVF of the lower limb form?

Answer 18

Usually iatrogenic in nature and result from catheter needle insertion or tributaries of the saphenous vein remaining un-ligated in an insitu bypass graft. Can also be caused by biopsy

Question 19

What is Burger’s disease?

Answer 19

Thromboangiitis obliterans. Most patients are primarily affected in the lower limbs. It is an inflammatory arteritis which initially affects small, distal arteries. Produces severe symptoms such as rest pain, ulceration and gangrene. Disease progresses proximally to involve larger distal arteries.

Question 20

What is fibromuscular dysplasia?

Answer 20

Non-inflammatory disease of arteries. It can affect arteries of the lower limb but is more common in the ICA and renal arteries

Question 21

What is Marfan syndrome?

Answer 21

Marfan syndrome involves the alteration of the elastic or connective tissue associated with arteries. Can result in pathologies such as aortic dissection/aneurysm

Question 22

What is Ehlers-Danlos syndrome?

Answer 22

Ehlers-Danlos syndrome produces arteries that are fragile and can haemorrhage with a high degree of fatality

Question 23

What is pseudoxanthoma elasticum?

Answer 23

May for non-significant stenosis in mid-sized arteries such as the femoral artery

Question 24

What is aortic coarctation?

Answer 24

• stricture of the aorta

- can occur in the thoracic or abdominal segments

Question 25

What is adventitial cystic disease?

Answer 25

- cyst formation in the adventitia - causes characteristic stenosis or occlusion of the artery - produces symptoms of claudication

Question 26

What is popliteal entrapment?

Answer 26

- results from abnormal anatomical arrangements of the popliteal artery - can cause it to be externally compressed by the surrounding muscles or fibrous tissue to cause stenosis during phases of limb movement during exercise

Question 27

Describe angioplasty and stenting in peripheral arteries.

Answer 27

- ballooning from within the lumen of a stenosis with or without stent placement is commonly used - puncturing the intima and creating a new flow channel within the arterial wall and exiting on the distal side 'subintimal' angioplasty

Question 28

List some types of arterial bypass grafts

Answer 28

- Fem-pop - above knee fem-pop - femoral-distal - femoral-tibial - aorto-bifemoral - aorto-iliac - femoral-femoral cross over

Question 29

What are bypass grafts made of?

Answer 29

Grafts bypassing proximal disease such as aortic or femoral are made of synthetic tube as veins are not considered large enough to cope with the high flow rates. Usually made of Dacron. Extra-anatomic bypass grafts are also usually made of Dacron Grafts from arteries above the knee to the popliteal or tibial arteries are usually constructed of a vein or PTFE. The GSV is most commonly used, but SSV, cephalic and basilic veins can also be used.

Question 30

Describe the two distinct bypass methods.

Answer 30

In situ grafts mobilise proximal and distal ends of the veins to anastomose to their respective arteries. Reversed graft is when the vein is removed and turned around before placing it back in the leg and forming the anastomosis.

Question 31

Why do we do ultrasound of the lower limb arteries?

Answer 31

- define the presence of pathology and document the degree of stenosis, extent and location - extend and location is documented by anatomical landmarks - degree of stenosis is estimated to identify significant lesions that may require repair

Question 32

What is the ankle brachial index?

Answer 32

ABI uses continuous wave Doppler to measure systolic BP in the upper and lower limbs. It is performed by applying blood pressure cuffs to the upper arms and lower calves above the ankle. The probe monitors radial or brachial pulses while the arm cuff is inflated and then deflated until the returning pulse indicates the systolic pressure. The patient is then exercised under standard conditions or until they can't continue or predetermined distance. The arm and high of the pedal pressures are repeated within the first minute and then by protocol. ABI is calculated by dividing the PTA or DPA pressure by the higher of the two brachial pressures. Pedal pressure is normally equal to or higher than brachial pressure. (= or > 1)

Question 33

What do low results of ABI mean?

Answer 33

In significant pressure-reducing lesions, the degree of ratio reduction is exaggerated. Degree of reduction in ABI is variable

Question 34

What are the pitfalls of ABI?

Answer 34

- calcification in arteries will resist compression and produce an artificially high pressure - calcification may prevent artery from occluding making measurements impossible - cannot specifically identify the location of a stenosis - less sensitive to the development of a stenosis when compared to Duplex scanning in monitoring bypass grafts

Question 35

What should a b-mode image look like of the lower limb artery?

Answer 35

- should display the wall of the artery - minimise as much artefact in the lumen as possible - artery must be seen in context of surrounding tissue

Question 36

What should a colour image look like of the lower limb artery?

Answer 36

- should aim to make the artery as horizontal across the screen as possible - achieving the angle as close to 90 degrees is the objective - set PRF scale so that the bulk aliasing is eliminated or so that there is a small degree of aliasing during systole