vascular Sara Flashcards
what is chronic limb ischaemia? (include pathophysiology)
A gradual reduction in the blood supply to a limb caused by atherosclerosis of vessels supplying the limb.
Atheroma builds up within the intima of the vessel resulting in stenosis of the vessel. This reduces blood flow. During times of exercise this blood flow is not enough and results in ischaemia and thus anaerobic respiration. lactate and K build up causing the individual cramping pain.
what are the risk factors for chronic limb ischaemia?
smoking - massive risk factor - increases platelet activation, fibrinogen levels, reduces HDLs and increases lipids
diabetes, HTN, hyperlipidaemia
FHx
associated with ischaemic heart disease and cerebrovascular disease
how does chronic limb ischaemia present?
intermittent claudication: pain/cramping gradually comes with activity and reduces rapidly with rest.
usually calf pain but can also be buttocks and thigh.
what are important differential diagnosis when considering chronic limb ischaemia?
spinal stenosis
acute limb ischaemia
muscle sprain
DVT
what do you expect to find on examination of someone with chronic limb ischaemia?
inspection: pale, poor skin condition (ulcers)
palpation: cool temp, weak foot pulses, slow cap refil . include palpation of abdo for AAA and popliteal fossa for popliteal aneurysm
listen for carotid bruits (associated)
always compare both legs
how can you investigate chronic limb ischaemia?
bloods: FBC (anaemia can aggrevate it), lipids and glucose (risk factors) , clotting.
ABPI
tredmill testing - walking brings on pain. Ask them to go uphill and if better consider spinal stenosis
feel calves for tenderness at rest - sprain/DVT
duplex USS - view stenosis
BP and ECG for risk factor
angiography - CTA or MRA
check for thrombophilia/homocysteine if young (<50)
where can atheromas be located to cause chronic limb ischaemia?
superficial femoral arteries - majority
calf arteries - mainly in diabetics
aorto-iliac arteries
what is leriches syndrome?
bilateral intermittent claudication
buttock claudication
erectile dysfunction
due to atheroma in the aortic bifurcation therefore affecting both internal and external iliac arteries.
what are the complications of chronic limb ischaemia?
necrosis /gangrene and sepsis and the need for amputation
this risk is higher for diabetics or those who continue to smoke.
how do we treat chronic limb ischaemia?
conservative: manage risk factors (stop smoking), exercise rehab
pharm: statins, aspirin, clopidogrel
percutaneous transluminal angioplasty
surgical bypass
how does exercise rehab help chronic limb ischaemia?
helps walking technique
improves collateral supply
improves capillary perfusion
what is percutaneous transluminal angioplasty?
helps chronic limb ischaemia
catheter put into vessel and balloon dilated to help reduce the stenosis +/- stenting.
patient has to be willing to change lifestyle otherwise disease will reoccur
how does surgical bypass work in chronic limb ischaemia?
use duplex USS to find a suitable vein for bypass. e.g. common femoral to popliteal. follow up and check with duplex.
what is ABPI? How is it performed?
ankle brachial pressure index. compares blood pressure at ankle to that in the arm to give a value about the degree of PVD.
put BP cuff around ankle. using Doppler find the foot pulse. inflate cuff till pulse has gone. slowly deflate and record the pressure which the pulse returns. this is the ankle systolic pressure.
find systolic pressure in arm
ABPI= ankle/brachial.
what do different values for ABPI mean?
>0.9 normal 0.8 - 0.9 mild 0.5-0.8 - moderate <0,5 = severe <0.4 = critical
chronic limb ischaemia
how can we make the ABPI more sensitive?
record after exercise. if the value drops it is more likely there is PVD
what does an ABPI of >1.4 suggest?
sometimes atherosclerosis results in calcification and hardening of the arteries. therefore they become less compressible with pressure and this will give an abnormally high ABPI. in this case the result is an inaccurate measure of limb ischaemia/ PVD
what is acute limb ischaemia?
sudden decrease in limb perfusion that threatens the viability of the limb
what are the clinical features of acute limb ischaemia?
sudden onset of 6Ps - pain, pallor, paresthesia, paralysis, perishingly cold and pulseless.
Colour is variable:
at first there may be pallor due to arterial spasm. Then the anaerobic respiration leads to release of vasoactive substances and vasodilation and so the limb can appear paradoxically red/ purple and mottling
unilateral
how can you tell the limb is still salvageable in acute limb ischaemia?
if the mottling blanches under pressure
what are the causes of acute limb ischaemia?
chronic limb ischaemia - i.e. atheroma which has progressed
embolism from MI, AF, prosthetic valve or aneurysm
thrombotic condition
trauma - compartment syndrome
what are the complications of acute limb ischaemia?
irreversible muscle necrosis and paralysis
need for amputation
repurfusion injury and compartment syndrome
electrolyte disturbances (release of K+ ) effects heart/gut
rhabdomyolysis - AKI
what is the Buergers test?
test for chronic limb ischaemia
raise leg and look for pallor - if pallor at 20 degree the ischaemia is severe. compare to the other leg
how can we examine for acute limb ischaemia?
look for sign of 6Ps
investigate cause e.g. AAA
what investigations should we do in someone presenting with acute limb ischaemia?
FBC, clotting, U and Es
serum lactate - assess level of ischaemia
thrombophilia screen if <50yrs and no risk factors
ECG - AF?
Doppler US
CT angiography
how does CT angiography work?
inject dye and this dye should flow through circulation
CT dye appears white and thus can see areas where there is stenosis or circulation is blocked.
how can you manage acute limb ischaemia?
high flow O2 - increase oxygenation to tissue
analgesia
IV heparin
emergency angioplasty, bypass surgery or amputation or embolectomy for emboli
monitor K+ and myoglobin levels
advice on risk factors
how does embolectomy work?
use a fogarty catheter and insert balloon through vessel and then dilate behind the clot and pull the clot out with the catheter and balloon.
requires general or local anaesthetic.
how does duplex Doppler and spectral Doppler USS work
duplex - red for arterial, blue for venous. allows you to observe flow
spectral shows speed and quality of flow
what is critical limb ischaemia?
chronic limb ischaemia has advanced to critical staged
defined by: rest pain >2 weeks, requiring opiates, ulcer/gangrene, ABPI <0.4
rest pain includes pain in foot at night that can be relieved by dangling foot out of bed (gravity)
what is an aneurysm?
A permanent dilation of a vessel more than 1.5x its normal size
what are the different types of aneurysms?
true - pathological degeneration involving all layers of vessel wall e.g. due to atherosclerosis
false/pseudoaneurysm - leakage of blood out of an artery into a cavity supported by connective tissue that is expansible and pulsatile.
what are the causes of aneurysms?
congenital - berry aneurysms of circle of willis
degenerative - atherosclerosis
connective tissue disorders - marfans and ehlers danlos
infective - mycotic aneurysms in infective endocarditis and syphilis
dissection
trauma
what is the pathophysiology behind an aneurysm?
loss of elastin and smooth muscle from medial wall and so artery can stretch and doesn’t recoil as much.
where is the body do aneurysms occur?
most common = aorta
then popliteal
also common femoral, intra-abdominal sphlanchnic, subclavian and carotid
what is Ectasia
Localised area of enlargement of a vessel but <1.5x normal size
what is arteriomegaly?
generalised enlargement of arterial tree
how do popliteal aneurysms present?
mainly asymptomatic
50% are bilateral
can get symptoms of complications:
- acute limb ischaemia if embolization occurs
- symptoms associated with rupture (rare)
how do you examine for a popliteal aneurysm?
flex knees and feel for popliteal pulse usually quite weak. IF you can feel a pulse an aneurysm should be suspected. feel for a pulsatile mass.
How can we investigate a popliteal aneurysm?
CT angiography - gold standard
USS duplex - differentiates between this and bakers cyst
should examine for AAA because often associated
what are the complications of a popliteal aneurysm?
main risk is embolization
Rupture is rare
how do you manage a popliteal aneurysm?
if >2cm or symptomatic, it should be treated due to risk of embolization
Hunterian ligation of popliteal aneurysm and bypass surgery - open surgery where the vessels is ligated and replaced with bypass graft
OR
endovascular stenting - can be done under local and thus preferred for unfit patients.
what is the risk of endovascular stenting in popliteal aneurysms?
stent thrombosis
aneurysm sac can fill through collateral vessels.
what causes femoral artery aneurysms?
percutaneous endovascular interventions
IV drug users who inject into groin