Topic 6- lower extremity arterial disease Flashcards
Define limb ischaemia
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
What is the most common cause of lower limb ischaemia?
Atherosclerosis
List some features of ischaemia
- 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
What is claudication?
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
What is the cause of claudication?
It is usually associated with atherosclerosis but can be caused by spinal canal stenosis, adventitial cysts and entrapment syndrome
What is critical limb ischaemia?
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.
What is rest pain?
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.
What are features of rest pain?
Features are pain while supine that is relieved by hanging the leg over the bed
Why does hanging the leg over the bed relieve rest pain?
This is thought to be due to the increase in hydrostatic pressure which is enough to provide sufficient pressure to re-perfuse the tissue.
Where do lower limb aneurysms occur?
Common femoral and popliteal.
What is a false aneurysm? `
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.
What are the 6 features of acute ischaemia?
Pulselessness Pallor Paresthesia Paralysis Poikilothermia Pain
What causes acute occlusion of an artery?
- embolisation from a proximal source
- thrombosis of an atherosclerotic artery or bypass graft
What is arterial thrombosis?
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
What is Klippel-Trenaunay syndrome?
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.
What is Parkes Webber syndrome?
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.
How do AV-fistulae form?
Formation mostly occurs due to trauma or related pathology such as erosion of an aneurysm, neoplasm or abscess
How do traumatic AVF of the lower limb form?
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
What is Burger’s disease?
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.
What is fibromuscular dysplasia?
Non-inflammatory disease of arteries. It can affect arteries of the lower limb but is more common in the ICA and renal arteries
What is Marfan syndrome?
Marfan syndrome involves the alteration of the elastic or connective tissue associated with arteries. Can result in pathologies such as aortic dissection/aneurysm
What is Ehlers-Danlos syndrome?
Ehlers-Danlos syndrome produces arteries that are fragile and can haemorrhage with a high degree of fatality
What is pseudoxanthoma elasticum?
May for non-significant stenosis in mid-sized arteries such as the femoral artery
What is aortic coarctation?
- stricture of the aorta
- can occur in the thoracic or abdominal segments
What is adventitial cystic disease?
- cyst formation in the adventitia
- causes characteristic stenosis or occlusion of the artery
- produces symptoms of claudication
What is popliteal entrapment?
- 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
Describe angioplasty and stenting in peripheral arteries.
- 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
List some types of arterial bypass grafts
- Fem-pop
- above knee fem-pop
- femoral-distal
- femoral-tibial
- aorto-bifemoral
- aorto-iliac
- femoral-femoral cross over
What are bypass grafts made of?
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.
Describe the two distinct bypass methods.
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.
Why do we do ultrasound of the lower limb arteries?
- 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
What is the ankle brachial index?
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)
What do low results of ABI mean?
In significant pressure-reducing lesions, the degree of ratio reduction is exaggerated. Degree of reduction in ABI is variable
What are the pitfalls of ABI?
- 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
What should a b-mode image look like of the lower limb artery?
- 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
What should a colour image look like of the lower limb artery?
- 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
