Quiz 2 Flashcards
how much of the cardiac output supplies the brain?
15%
how much of the flow from the CCA enterws the normal ICA?
80%
brain has a high or low metabolic rate?
high-little circulaory reserve
where does the brain store oxygen or glucose?
Brain has no significant oxygen or glucose stores
what is the brain dependant on?
the vascular system
short episodes of interuppted cerebral flow can bring on what?
symtoms of cereral dysfuction
how long does it take for cellular death to occur?
3-8 minutes
how does blood flow with resistance?
the path of least resistance
what is resistance affected by?
length and width
does length or width have the greater effect?
long narrow vessel has the greatest resistance and a short wide has the least resistance
is length or width more limiting becuase of Poiseuille’s Law?
width
what does adequate arterieal perfusion rely on?
- systemic blood pressure
- cardiac output
- blood volume
If circulation is compromised by atherosclerotic disease _______________________
compensation may be insufficient
what does circulation compromised by atherosclerotic disease lead to?
regional or diffuse hypoxia or anoxia
what has a vital role in arterial occlusion?
collateral circulation
what testing is available for collaterization?
- duplex US
- angiography
- MRA (MRI angiography)
- CTA (CT angiography)
when evaluating the symtoms of cerebrovascular insufficiency what must clinicians be aware of?
extent or lack of collaterization
do collaterals develop fast or slow?
slowly often over a period of years
do patients reveal symtoms of cerebrovascualr disease with total occlusion of ICA?
no
why does collateral circulation develop?
becuase of a change in the pressure gradient between the vessels, caused by a stenosis
what happens to pressure, distal to a stenosis?
drop in pressure
when may blood vessels abandon their normal flow routes to take advantage of the new,lower pressure route?
if the pressure drops enough to attract flow from a vessel situated further down the line
(subclavian steal syndrome)
what is opening of collateral pathways dependant on?
patient age and time sequence of occlusion
in older individuals, collateral pathways may already be _____________
hypoplastic or atherosclerotic
when do collateral pathways have a better chance of developing?
with slow evolving atherosclerotic occlusion
when are collaterals not able to adapt?
not able to adapt rapidly enough to sudden occlusions such as emboli
where does our body develop alternate routes for blood flow?
each hemisphere of the brain (these are called collaterals)
what do the most common collateral pathways involve?
the circle of willis
what are the 3 major collateral routes?
- other side of the circle of willis
- the posterior cerebral circulation
- the external carotid artery branches
how many patients have a complete circle of willis (no varients)
50%
what does a totally occluded left ICA result in?
decrease in flow to the left hemisphere of the brain
describe the pathway of blood to the left from the other side of the circle?
Right CCA to right ICA to right ACA,across the anterior communicating artery ,then retrograde down the left ACA to the left MCA to perfuse the left hemisphere
describe the pathway from the posterior circulation?
Vertebral artery flow enters the basilar artery,to the left posterior cerebral artery,across the left posterior communicating artery to the distal left ICA and finally to the left MCA
describe the pathway from the ECA?
The left ECA to an ECA branch(superficial temporal,maxillary or facial),retrograde down an ICA branch(supraorbital,nasal or frontal) to continue retrograde flow down the ophthalmic artery,into the carotid siphon and finally to the MCA to perfuse the left side of the brain
what is the second most importnat source of collateral flow?
next to the circle of willis, the anastomosis between branches of the ECA and ICA via the orbital and ophthalmic arteries
what is the only branch of the ICA to give off branches that leave the intracranial space?
ophthalmis artery
what branches are apart of the peri-orbital circulation?
frontal and supraorbital arteries and the nasal artery
what do the peri-orbital arteries of the ICA communicate with?
branches of the superficial temporal artery as well as the facial artery
what sites of communication become important in cases of severe obstruction or occlusion of the ICA?
periorbital branches of the ICA communication with the superficial temporal artery and facial artery
collateral branches:
- lacrimal
- supraorbital
- anterior and posterior ethmoidal
- medial paplebral
- frontal
- dorsal nasal artery
what happens when occlusion occurs in the ICA?
flow in the opthlamic artery becomes retrograde in order to supply the brain
what is #1 less important collateral possibilities?
the occiptal branch of the ECA communicating with the atlantic branch of the vertebral artery
what is the #2 less important collateral possibilities?
the deep cervical branch of the subclavian artery communicating with the more proximal branches of the vertebral artery
what is the #3 less important collateral possibilites?
the “rete mirabile”consisting of a network of transdural arteries which may anastomose across the subdural space with the tiny arteries covering the surface of the brain
what happens with CCA occlusion?
flow reverses in the ECA and flows into the ICA in the opposite direction toward the brain
what system is included in the duplex exam of the carotids?
vertebral artery disease
what diagnostic information is most essential with vertebrals?
presence or absence of flow and direction of flow
how much of cerebral blood flow does the vertebral basilar system provide?
20-30%
in the case of vertebral occlusion near its origin flow is ______________-
shunted to the thyrocervical and costocervical trunks and compensatory enlargment of the opposite vertebral artery occurs
where do the vertebral arise from?
subclavian arteries
where in the cervical spine does the verbetral coarse?
C6-C2
what do the vertebral arteries form?
the basilar artery
what is a normal varient with the vertebrals?
left vertebral artery may arise directly from the aortic arch-6% of patients
how does the basilar artery connect to the circle of willis?
via the PCAA
symtoms and sign of posterior circulation ischemia
slide 6 collateral 2
what is the flow patterns of the vertebrals?
low resistant-similar to the ICA
what do the velocities range in the vertebrals?
20-60 cm/s
below ___________may indicate vertebral insufficiency due to prox or dist occlusion
20 cm/s
what may higher than normal velocities indicate?
stenosis
what may high volume flow states indicate?
a compensatory flow pattern as seen in collateral flow
what may high volume flow states be seen in some patients?
may be hypoplastic or absent on some patients
how often is right vertebral imaged?
80% of the time
how often is the left vertebral imaged?
60% of the time
what is the least likely level of disease in vertebrals?
mid portion (seen with least difficulty)
what vertebral artery is more commonly larger?
left
________ vertebrals are hypoplastic
7-10%
what doppler parameters are set for vertebrals?
low flow states
what flow direction should the vertebrals be?
antgrade (toward the head)
why do we look at spectral in the vertebrals?
rule out SSS
what is the normal flow pattern in the vertebrals?
- low resistant
- window not always present
what are the velocites in the vertebrals?
40-60 cm/s
what does a high resistant vertebral flow pattern with no diastolic flow imply?
- distal VA stenosis or occlusion
- hypoplastic VA
what are the S/S of a stenosis in the vertebrals?
dizziness and unsteady walking
what is indicative of vertebral disease?
increased compensatory flow-PSV completely reversed flow
describe the appearance of subclavian steal syndrome?
Lt SCA origon occlusion or high grade stenosis
-flow is reversed in ipsilateral vertebral artery
when does SSS result?
when the short low resistant path becomes a high reistant path due to narrowing
when may compensatory flow be seen in the vertebral artery?
presence of ipsilateral carotid occlusive disease
what shows the vertebrals ability to maintain flow via circle of Willis to cerebrum?
increased peak velocities
what is subclavian steal syndrome?
hemodynamically significant stenosis or occlusion in proximal subclavian arteries can result in the vertebral acting as a collateral pathway
where is SSS more commonly seen?
on the left side
what is the sonographic appearance of SSS?
-high PSV >500cm/s
-loss of normal triphasic signal
-color aliasing
-decreased ipsilateral brachial artery systolic BP
-40 mmHg difference between arms
damped flow distally (monophasic)
-reversed flow ipsilateral VA
why does flow reverse in the VA for SSS?
to supply the ipsilateral arm
impending steal
incomplete reversal of signal
what will happen when the VA has not completely reversed?
exercising the arm will completely reverse the signal below the baseline
what is a syndrome?
The aggregate of signs,symptoms or other manifestations to constitute the characteristics of a morbid entity
what serves to increase the pressure drop across a stenosis?
- Subclavian steal syndrome begins with a stenosis near the origin of the subclavian artery or the innominate artery on the right side
- The presence of a significant stenosis results in a pressure drop distally
- further decrease in upper extremity resistance when exercise occurs due to vasodilation of the distal resistance bed
- the increase in subclavian artery flow that occurs secondary to exercise
what happens when there are so many pressure drops with SSS?
the pressure in the subclavian artery falls below that of the junction of the 2 vertebral arteries at the base of the brain and blood flows retrograde down the vertebral artery to supply blood to the arm
what will happen if the left side has SSS?
the left vertebral has retrograde flow, the contralateral vertebral and CCA will have increased flow. this keeps the pressure in the circle of willis constant
which side has a greater impact on cerebral hemodynamics and why?
right side (innominate) artery becuase of the additional involvment of the right CCA
in right sided innominate artery stenosis what CCA will have a lower perfusion pressure?
right CCA will have a lower perfusion pressure as a result of the proximal innominate artery stenosis
what is an accurate way to diagnose SSS?
the use of doppler (90-100% accurate)
what is the key to successfully diagnosing the presence of steal syndrome?
the reversal of flow in the VA (the final stage)
what is an early stage of SSS?
Prior to constant flow reversal there is a deceleration of antegrade flow during systole with retrograde flow only in diastole
-usually these are seen in periods of exercise
what happens with flow when SSS is on left side?
no flow gets to vertebral artery and left arm do blood from the right vertebral enters the left vertebral and flows back to supply the arm
what does impending reversal of flow look like on spectral?
bunny sign
what is reactive hyperemia of the forearm?
in notes
clinically, what do people with SSS have?
- often a loud supraclavicular bruit
- always a reduced pulse and blood pressure in affected arm
what completes the diagnosis of SSS if everything else is postive?
brachial artery pressure
what will happen to the normal triphasic waveform distal to the subclavian stenosis?
will be damped due to the drop in pressure and flow
what does the flow pattern look like distal to a stenosis?
loss of high resistant, high pulsatility flow of the distal SCA
SSS hemodynamic changes normal side:
- PSV-120 cm/s, no turbulence
- distal flow normal
- brachial pressure normal (120/80 mm Hg)
- vertebral artery will have increased flow volume with increased velocity
SSS hemodynamic changes abnormal side:
- PSV >400 cm/s or occluded completely
- distal flow is damped
- brachial pressure is low (80/50 mmHg)
- vertebral artery will have completley reversed flow or partially
what is thoracic outlet syndrome?
entrapment syndrome that may contribute to various degrees of limb ischemia
what is there a potential of in thoracic outlet syndrome?
compressing the subcavian artery and brachial nerve plexus
what is paget-schroetter syndrome?
refers to effort induced DVT of the upper extremity veins in young patients
what is paget-schroetter syndrome classified as?
a thoracic outlet syndrome
what do patients present wiith for thoracic outlet syndrome?
patient presents with an upper extremity circulatory problem such as cold, painful, or numb extremity
what could repeated compression from TOS cause?
injure the intima causing thrombus formation
what is uncomplicated TOS?
- no thrombus, plaque or aneurysm formation
- may be caused by nerve compression
when testing for TOS how is it done?
segmental blood pressures and pulse volume waveforms are obtained with the limb in neutral position then repeated in the position they feel discomfort then repeated with head and arm in extreme postions.
A CHANGE IN BP’S OR PVR’S SHOULD OCCUR
where are BP’s taken when testing for TOS?
obtained at proximal and distal brachial artery levels
what should happen with the radial artery with thoracic outlet syndrome?
radial artery signal goes flat
what could mimic TOS?
mechanical compression of an artery by:
- skeletomuscular system
- inflammatory mass
what is a common site especially in young atheletes for one form of mechanical compression?
popliteal artery behind the knee joint
what may result in diminished flow to the calf and foot?
hyperextension of the knee or active plantar flexion of the foot
what compresses the popliteal artery?
medial head of the gastrocnemius muscle
what happens to pressure and veloccity when the poplieal artery is compressed?
drop of atleast 20 mmHg and tibial artery velocities are reduced
when is popliteal entrapment diagnosed?
when certain patient positions are responsible for loss or diminution of arterial pulsations with the doppler device
anterior compartment syndrome
anterior tibial compartment
-this may result in arterial compression and subsequent ischemia distal to the site of arterial compression
what is one of the frequent manifestations of tissue ischaemia?
blue toe syndrome
what causes blue toe syndrome?
occlusion of small vessels and usually iccurs in elderly men who undergo an invasive vascular procedure
what is blockage in blue toe syndome caused by?
either cholesterol crystals or a lump of plaque getting stuck in the small vessels
does blue toe syndrome happen in both feet?
may affect one or more toes but is usually confined to one foot (develops suddenly and rapidly)
what can happen if blue toe syndrome is left untreated?
gangrene can set in
what is focused on when diagnosing blue toe syndrome?
concenrates in finding the source of the problem, where the embolus blockage came from
what is the usual cause to a blockage in the feet?
usually there will be a problem further up the arterial tree in one of the proximal bloos vessels such as an aneurysm or plaque deposits-atherosclerosis
what are the diagnostic tools of choice for blue toe syndrome?
ultrasound scans and CT angiograms
what is stenting?
a mesh tube is inserted into a blood vessel to hold it open and prevent restriction of blood flow
what is bypass surgery?
where blood flow is diverted around major arteries that are narrow or partially blocked
what are anti-coagulants and anti-platelet therapy?
these can help in the short time but are associated with a high recurrence rate of blue toe syndrome
what is raynauds disease?
causes some areas of your body-such as your fingers and toes- to feel numb and cold in responce to cold temp or stress
what happens to your blood vessels in raynauds disease?
smaller arteries that supply blood to your skin narrow, limiting blood circulation to affected areas (vasospasm)
who is more likely to develeop raynads syndrome?
women and those living in colder climates
what is the treatment of raynauds syndrome?
depends on its severity and whether you have other health conditions
what are some signs and symptoms of raynauds syndrome?
- cold fingers or toes
- color changes in skin
- numb, tingling pain when warming
what is the order of colour of your skin in raynauds syndrome?
white
blue
red
what may develop in raynauds syndrome?
a sore, ulcer or infection in onw of your affected fingers or toes may develop
another name for primary raynauds?
raynauds disease
another same for secondary raynauds?
raynauds phenomenon
what is the most common form of raynauds?
primary raynauds/raynauds disease
what is primary raynauds?
Not the result of an underlying associated medical condition that could provoke vasospasm
what is secondary raynauds?
- Less common form , caused by an underlying problem
- It tends to be more serious due to the underlying disease/condition
when do signs and symptoms occur for raynauds?
secondary usually appear later in life (around age 40)
connective tissue disease?
- scleroderma
- lupus
- rheumatoid arthritis
- Sjogren’s syndrome
read over slide 36
arterial syndromes
what is the cold simulation test designed to trigger?
symtoms of Raynaud’s and is used in conjuncttion with other tests to diagnose the condition
what are the steps for a cold stimulation test?
- a small temperature-measuring device is attached to your fingers with tape
- your hands are place in ice water to trigger symtoms
- the measuring device records how long it takes your fingers to return to normal body temperature
- arterial study of the upper extremirty tot R/O obstruction or TOS may be done
what is nutcracker syndrome?
vascular compression disorder. Compression of the left renal vein between the SMA and aorta
what can nutcracker syndrome lead to?
- renal venous hypertension, resulting in rupture of thin-walled veins into the collecting system with resultant hematuria
- left testicular pain or LLQ pain in women
what can happen as a result of nutcracker syndrome?
nausea and vomiting due to compression of splanchnic veins
what does an unusual manifestation of NCS include?
varicocele formation and varcose veins in the lower limbs
what is a frequent finding in varcocele?
nutcracker syndrome
what should Nutcracker syndrome should be routinely excluded as?
a possible cause of varicocele and pelvic congestion
what does nutcracker syndrome look like sonographically?
- lt renal enlargment
- persistant hematuria
- proteinuria
- hypertention
- RV thrombus
what are surgical approaches for nutcracker syndrome?
- Nephrectomy
- nephropexyr
- enocaval reimplantation
- intravascular stent
what is leriche syndrome?
blockage in the lower part of the aorta just before the starting point of the common illiac arteries
what are the risk factors for leriche syndrome?
atherosclerosis and smoking
what are the 3 main symptoms of leriche syndrome?
- claudication of buttock area
- impotence (failure to achieve or maintain an erection in males)
- decreased pulses in lower limbs
what helps with the diagnosis of leriche syndrome?
the Ankle Brachial Index
complete arterial doppler study of the Aorta/Iliac region and the peripheral arteries should be done
what will you see with leriche syndrome?
distal aorta and bifurcation will be occluded
what is marfan’s syndrome?
genetic disorder that affects the body’s connective tissue
what body parts are usully affected by marfan’s syndrome?
- heart
- blood vessels
- bones
- joints
- eyes
what can be life threatening with marfan’s syndrome?
aortic aneurysm
dissection
what appearance do people with marfan’s syndrome have?
- long arms and legs
- tall, thin body type
- long, thin fingers
what does the longitudinal image of the CCA show?
- sharp line (spectral reflection) that emanates from the intimal surface
- the black line peripheral represents the tunica media
- the outermost white line in the tunica adventitia
can we see the walls of the veins?
nope
what is thickening of the intima-media (>0.9) associated with?
atherosclerosis
increased risk of cardiovascular disease
what factors are involved by thickeneing of the IMT?
- hemodynamics
- shear stress
- blood pressure
what is the waveform of the CCA?
- medium pulsatility
- close to the baseline
- low diastolic flow
- sharp upstroke
what is the waveform of the ICA?
- lower pulsatility
- window
- high diastolic flow
what is the waveform of the ECA?
- higher pulsatility
- higher upstroke
- closer to baseline
- relatively lower diastolic flow
how to find ICA?
vessel with the bulb is the ICA and laterally located
how to find ECA?
narrower vessel and medially located
what spectral waveform could demonstrate carotid stenosis?
- spectral broadening
- high velocities
- turbulent flow below baseline
waveform of the vertebrals?
- low pulsatility
- similar to ICA with low velocity
- forward flow throughout diastole
- travels cephalas through TRV formaina C6-C2
subclavian and innominate artery waveform?
- High pulsatility
- Sharp systolic upstroke
- Triphasic signal(normal)
- May be multiphasic
- Reverse diastolic component
- Forward diastolic component
what do we measure for PSV when there is an irregular heartbeat?
after the most normal QRS interval
what is the most common arrhythmia seen on vascular US?
atrial fibrillation
waveforms in atrial fibrillation have varying ___________
amplitude
pulsus bisferans
component of reverse flow
what is aortic regurgiatation seen as?
prominent notch in the waveform (but this can be seen in young patients)
what is considered tachycardia?
> 100 BPM
what does PSV and EDV look like for tachycardia?
The PSV is decreased while the EDV is increased
what is happening with tachycardia?
- left ventricular volumes are decreased due to the limited duration of diastolic filling
- the heart cannot pump enough blood to meet body’s need
what is considered bradycardia?
<60 BPM
what is bradycardia a sign of a problem of?
problem with hearts electrical system
what is happening with bradycardia?
-the heart does not pump enough blood to meet the bodies needs
what does PDV and EDV look like for bradycardia?
PSV wil be elevated and EDV will be low
what is an alternative to carotid endarectomy in high risk patients?
carotid angioplasty
why are serial follow up exams recommended for angioplasty?
re-stenossis can occur
what is expected in a carotid stent?
smooth velocity increase
what is not normal in carotid stents?
regions of abrupt increased PSV and post stenotic turbulence
why are velocites higher in carotid stents?
due to loss of wall eleasticity and increased “stiffness” where the stent is located
what is carotid endarectomy?
operation during which the vascular surgeon removes the plaque from lining of your carotid artery
who has a endarectomy done?
- previous TIA’s and a blockage >50%
- asymtomatic patients with blockage >60%
what are complications of endarterectomy?
restonosis
stroke
what do we expect to see endarterectomy?
- minor wall contours and loss of the intimal/media stripe at repair site and closure sutures appear bright
- wall thickening may occur, intimal flaps, and any level of restenosis or occlusion on follow up
- disturbed flow: PSV ratios are most accurate
what indicates an intracranial ICA stenosis-siphon level?
a high resistant flow pattern in the mid-distal ICA
what is renal artery stenting?
a procedure to open the renal arteries
what is the most common cause for renal artery narrowing?
atherosclerosis or fibrous disease of the arteries
when is renal artery stenting done?
during a procedure called angioplasty
what is angioplasty?
inserting a small cathedar in the diseased renal artery
what is the treatment of chronic mesenteric ischemia?
Bypass surgery
how does bypass surgery work?
the vascular sugeon bypasses the narrowed or blocked section of the artery by creating a new avenue for blood flow using either a vein from another part of the body (bypass graft) or a tube made from synthetic material
is mesenteric bypass an open surgery or minimally invasive?
major operation done through an incision in the abdomen
when can angioplasty and stenting be done?
sometimes preformed at the same time as an angiogram
what is the treatment for acute mesenteric ischemia?
an emergency procedure
what may be injected dring an angiogram?
thrombolytic agents and other clot-dissolving medications. Sometimes these can dissolve the clot
what may happen during surgery of acute mesenteric ischemia?
some parts of the intestine may be damaged beyond repair and must be removed
what do we do if a patient has a high bifurcation?
use a curvilinear probe and try power doppler
what do we do if a vessel is straight up and down?
remove angle correct and shoot straight down the tube
what do we do in low flow states/trickel flow?
- lower the PRF
- increase the color gain
- use power doppler
