Peripheral Vascular Disease Flashcards
Define atherosclerosis
Which arteries does it affect?
Hardening and narrowing of arteries due to accumulation of lipids in the intima of medium & large sized arteries resulting in the thickening and hardening of arterial walls
State 3 components of an atherosclerotic plaque
(recap pathological processes)
- Cells: macrophages, leucocytes, smooth muscle cells
- Intra & extra cellular lipids
- Extracellular matrix: collagen, elastin, proteoglycans
Remind yourself of the pathophysiology of atherosclerosis
Atherosclerotic plaque formation has two steps: formation of fatty streak followed by formation of a simple plaque
Fatty Streak
- Chronic endothelial insult leads to endothelial dysfunction/damage
- Lipids, mainly from LDLs, and monocytes accumulate in intima
- Lipids are oxidised and ingested by macrophages to form foam cells
- Foam cells secrete cytokinies which attract more inflammatory cells and stimulate smooth muscle proliferation
- Smooth muscles migrate to lesion from media and start to proliferate- now called a fattty streak
Formation of simple plaque
- Number of foam cells & SMC increases causing plaque to grow
- Some smoooth muscle cells take up lipids
- Smooth muscles cells lie over plaque, beneath endothelium, forming a roof
- Roof reinforced by collagen, elastin & other amtrix proteins to form fibrous cap
- Endothelium stretches as plaque continues to grow creating gaps which platelets adhere to
- Centre of plaque undergoes necrosis
- Dead cells release cholesterol and cholesterol crystals appear in plaque
- Small blood vessels grow into plaque from adventitia
Remind yourself of at least 5 (out of 8 ways) a plaque can become complicated
- Ulceration: fibrous cap eroded from underneath and atheroma core, which is highly thrombogenic, is exposed
- Thrombsis on plaque: often on ulcerated plaque
- Spasm at site of plaque: thrombi release vasoconstrictors
- Embolisation
- Calcification
- Haemorrhage: if one of new vessels in plaque ruptures it can suddenly expand the plaque leading to oclusion or alternatively the pressure from haemorrhage may cause plaque to rupture
- Aneurysm
- Rupture of atherosclerotic artery
Summarise the process of atherosclerosis
- Endothelial dysfunction/damage due to chronic inflamation and activation of immune system in arterial wall
- This causes accumulation of lipids in intima of medium & large arteries and causes further inflammation
- Plaque formation
- Plaques can become complicated and casue:
- Stenosis
- Rupture giving off a thrombus which blocks a distant vessel
State some risk factors for atherosclerosis
Highlight which is greatest risk factor
- Age
- Family history
- Male
- Hypertension
- Smoking (x9) *BIGGEST!!
- Alcohol
- Poor diet (high trans-fat, little fruit & veg intake, little omega 3 consumption)
- Hypercholesterolaemia
- Hyperlipidaemia
- Low exercise
- Obesity
- Diabetes
Explain why smoking is a risk factor for peripheral arterial disease
Numerous ways in which smoking increases risk of peripheral arterial disease:
- Nicotine causes vasopasm of vessels
- Carbon monoxide, present in inhaled smoke, is taken up by haemoglobin to form carboxyhaemoglobin which dissociates slowly meaning the haemoglobin is unavailable for oxygen carrying and hence contributes to tissue hypoxia
- Increases platelet adhesion & fibrinogen levels which increase risk of thrombosis formation
- Decreased HDL, increases lipids
State some potential complications/end results of atheroscerlosis (i.e. what can it cause/lead to)?
- Angina
- ACS
- TIA & stroke
- Peripheral arterial disease
- Chronic mesenteric ischaemia
What are the 3 main patterns of presentation of peripheral arterial disease we see?
- Intermittent claudication
- Critical limb ischaemia
- Acute limb-threatening limb ischaemia
Define peripheral arterial disease
Atherosclerosis, causing narrowing, of the arteries supplying the limbs & periphery
Define critical limb ischaemia
End stage of peripheral arterial disese where there is an inadequete supply of blood to the limb to allow it to function normally at rest
Define intermittent claudication
Pain that occurs during exertion due to ischaemia in a limb; relieved by rest. Typically a crampy, achy pain associated with muscle fatigue.
Pts typically describe the pain in their calf when walking beyond a certain intensity.
Which muscles are most commonly affected by intermittent claudicaiton?
Calf muscles (although more proximal muscles may be affected)
Explain why peripheral arterial disease can lead to intermittent claudication
Narrowing of arteries leads to decreased blood flow to muscle
State some differential diagnosis for pain in lower limb during exertion
- Spinal stenosis
- Lower limb arthritis
- Musculoligamentous injury
- Acute limb ischaemia/acute on chronic limb ischaemia
Which arteries in lower limb most commonly have atheroma?
- Superficial femoral artery (80%)
- Aorto-iliac (15%)
- Calf arteries (5%)
80% of pts present with calf claudication, 18% present with calf, thigh and buttock claudication. 2% present with Leriche’s sydnrome.
What is Leriche’s syndrome?
Symptoms due to occlusion in distal aorta or proximal common iliac arteries causing triad of:
- Bilateral thigh & buttock claudication
- Absent femoral pulses
- Male impotence
State some key questions to ask when taking a history from pt with suspected peripheral arterial disease
What is the ‘claudication distance’?
Distance someone can walk before claudication occurs
Discuss what you might find on examination of someone with peripheral arterial disease
- Weak peripheral pulses
- Radial
- Brachial
- Carotid
- Aorta
- Femoral
- Popliteal
- Dorsalis pedis
- Femoral
- Delayed capillary refill
- Pallor
- Cold
- Skin changes (e.g. ulceration, hair loss [not mvery accurate/useufl])
- Bruits e.g. carotid
- Buerger’s Test
What classification is used to grade chronic leg ischaemia?
Describe this classification
Fontaine classification
For ABPI, discuss:
- What it is/definition
- How it is calculated
- Normal & abnormal result
- Ratio of systolic blood pressure in ankle vs the arm
- Doppler probe held over brachial artery and BP cuff inflated to occlude flow; as cuff is deflated doppler signal reappears and systolic BP is recorded. Similar pressure readings taken from dorsalis pedis & posteiror tibial arteries with a cuff just above the ankle. ABPI should be measured in each leg. See equation in image:
- Results (different places say different things). Teach me surgery says:
- Normal >0.9
- Mild 0.8-0.9
- Moderate 0.5-0.8
- Severe <0.5
If going to remember one number remember <0.9 = arterial disease
Discuss the management of intermittent claudication
- Lifestyle:
- Stop smoking!!
- Reduce alcohol
- Healthy diet
- Exercise
- Weight loss
- Exercise rehabilitation/supervised exercise programme
- Optimise control of comorbidities (hypertension, diabetes etc..)
- Pharmacological:
- Statin: atorvastain 80mg (ALL)
- Antiplatelet: clopidogrel 75mg (ALL)
- Naftidrofuryl oxalate (consider in those with poor QoL)
- Endovascular revascularisation= angioplasty +/- stent (shorter segments <10cm, high risk, aortic-iliac disease)
- Surgical revascularisation (longer lesions >10cm, multifocal disease, disease that is purely infrapopliteal):
- Bypass with autologous vein or prosthetic material
- Endarterectomy
Describe Buerger’s test
What may you see in someone with peripheral arterial disease?
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 goes pale is termed Buerger’s angle; an angle of less than 20 degrees indicates severe ischaemia
What is sunset foot?
Idea that chronic critically ischaemic limbs may appear pink due to compensatory vasodilation the so-called sunset foot
Ischaemia in acute life-threatening limb ischaemia may be due to thrombus or emboli; state some features that may suggest each
State the three main types of waveform we hear/see on doppler ultrasound
Which is best?
- Tri-phasic
- Bi-phasic
- Mono-phasic
Triphasic is best, monphasic is worst.
*NOTE: in young health people may hear/see more than triphasic
Explain the shape of a triphasic waveform
- First peak= peak systole
- Second peak (negative) = early diastole (some retrograde flow)
- Third peak (positive)= late diastole, artery contracts to propel blood forwards
*Go on youtube and remind yourself of how tri-, bi- and mono- phasic sound
