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49 Cards in this Set
- Front
- Back
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What are flow separations? |
- results from changes in the geometry and direction of the vessel with or without intra-luminal disease or because of curves - it is caused by the loss of laminar flow - has areas with stagnant or little movement (carotid bulb, any bifurcation) |
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What is Hollenhorst plaque? |
- it is a cholesterol emboli seen on opthalmoscopic exam within the retinal artery branches - possible source of the emboli is the ipsilateral carotid artery |
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What is a subclavian steal? |
blood flows retrograde (down the neck away from the brain) down the vertebral artery secondary to a subclavian steal or innominate stenosis or occlusion |
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Where is the blood stolen from in a subclavian steal? |
the blood is stolen from your brain to feed your arm |
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What are the symptoms of a subclavian steal? |
- patient usually asymptomatic - patient may have posterior circulation symptoms (bilateral complications) - decreased pulses in the affected arm with arm claudication being rare - surgical treatment may include a bypass graft or endarterectomy |
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What is the brachial blood pressure of a person with subclavian steal? |
brachial blood pressure difference of 15-20mmHg OR greater from one side to the other |
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What is the brachial pressures of a person with partial subclavian steal? |
- usually off MORE than 15-20mmHg
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What is the waveform of a person with partial subclavian steal? |
abnormal vertebral waveform - waveform is not retrograde - end diastolic component of the waveform is usually larger than the peak systolic |
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What is the Pourcelot study? |
- used when you suspect partial subclavian steal |
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How do you perform the Pourcelot study? |
- place a pressure cuff around arm with lower BP or side with the abnormal vertebral waveform - inflate the cuff to 10-20 mmHg above the highest brachial and leave on for 3 minutes - scan vertebral getting the best waveform possible - after 3 minutes, release all the air out of the cuff and watch to see if the vertebral waveform changes |
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What are the capabilities of periorbital doppler (indirect)? |
can detect hemodynamically significant lesions (HDSL) of the ICA by evaluating the flow in some of its terminal branches around the eye |
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What are the limitations of periorbital doppler (indirect)? |
- only diagnostic in cases of HDSL - cannot differentiate an occlusion from a tight stenosis - technically dependent |
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How do you perform periorbital doppler (indirect)? |
- patient should be supine with eyes closed - *flow in the frontal artery should be towards the probe (antegrade)* |
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What type of the transducer should you use for periorbital doppler (indirect)? |
use an 8-10 MHz Doppler locate the frontal artery at the inner canthus of the eye |
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What arteries should you compress with performing periorbital doppler (indirect)? |
- superficial temporal artery - angular artery - facial artery - infraorbital artery |
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What are the normal findings for periorbital doppler (indirect)? |
- antegrade flow in the frontal artery - compression of the superficial, angular, infraorbital, facial arteries should not decrease, diminish or reverse flow |
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What are the abnormal findings periorbital doppler (indirect)? |
- retrograde flow in the frontal artery is consistent with a HDSL of the ipsilateral ICA - diminished or reversed flow during compression suggest that flow into the frontal artery is from the vessel being compressed |
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How does oculopneumoplethysmography (OPG) work? |
- measures ophthalmic arterial systolic pressure (OSP) by applying a vacuum to the eye - the vacuum distorts the shape of the eye, intraocular pressure increases to the point at which it turns off arterial inflow - the pulse waveforms reappear as the vacuum is slowly decreased and recorded on a strip chart |
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Where are the eye cups placed for OPG? |
eye cups are placed on the lateral sclera (whites of the eyes) and the vacuum is applied |
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What are the contraindications of OPG? |
- allergies to local anesthetics - eye surgery within last 6 months - retinal detachment - acute unstable glaucoma |
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What is the normal ophthalmic systolic pressure (OSP) and how much can it be off by? |
A normal ratio of ophthalmic to systemic pressure should be: OSP - 39 ÷ brachial pressure (BSP) ≥ 0.430
Ophthalmic systolic pressures should not differ by: ≥ 5mmHg |
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What is the nyquist limit? |
it is the limitation of the ultrasound machine
nyquist frequency = 1/2 PRF |
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What type of transducer and angle should be used for transcranial doppler (TCD)? |
- transducer: 2MHz pulsed doppler with spectrum analyzer - the assumed angle of insinuation is zero degrees |
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What three windows are used to access the intracranial vessels of TCD? |
- transtemporal - transorbital - transforamenal (suboccipital approach) |
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What vessels can be seen with a unilateral transtemporal approach of TCD? |
- middle cerebral artery - anterior cerebral artery - posterior cerebral artery - internal carotid artery |
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What vessels can be seen with the transorbital approach of the TCD? |
- ophthalmic - carotid siphon |
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What vessels can be seen with the transforamen approach (foramen magnum) approach of the TCD? |
- intracranial vertebral - basilar artery |
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How do you accurately identify a vessel during TCD? |
- appropriate sample volume size and depth - knowledge of the direction and velocity of blood flow - relationship of the various flow patterns to one another |
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How should a patient be positioned during TCD? |
- supine - examiner should sit at the head of the patient and arrange the equipment for max comfort and support - patient should be calm, but not allowed to go to sleep
- allowing the patient to sleep may result in increased mean flow velocity due to increased CO2 |
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What are the characteristics for probable occlusion of the ICA? |
- ECA may take on some flow characteristics of the ICA (high diastolic flow) - little or no diastolic flow in the CCA
(*note: the two listed above happen in two separate scenarios, not at the same time*) |
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What is spectral broadening? |
it occurs when the window during turbulent flow is filled with all the extra velocities |
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Why might over estimation of the disease process occur? |
- artifact is mistaken for plaque
- accelerated flow is mistakenly attributed to a stenosis, other causes of increase flow: tortuous vessel (blood speeds up on turns), collateralizing for ipsilateral or contralateral disease
- inappropriate dopple angle: over estimation of the angle of incidence will result in overestimation of the velocity |
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Why might under estimation of the disease process occur? |
- very low level echoes of soft plaque may not be appreciated - accelerated flow may be missed unless the vessel is carefully interrogated - underestimation of the angle of incidence will result in underestimation of velocity |
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What are the characteristics of ECA? |
- usually medial - high resistant waveform (low end diastolic flow) - can see take offs - usually smaller - temporal tap |
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What are the characteristics of the ICA? |
- usually lateral - low resistant wave form (high end diastolic flow) - cannot see take offs - usually larger - important to show stenosis or occlusion |
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What are the symptoms of anterior circulation? |
- unilateral paresis - unilateral paresthesia or anesthesia - dysphasia (impaired speech) or aphasia (inability to speak) - amaurosis fugax - behavior changes |
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What are the symptoms of posterior circulation? |
- vertigo - ataxia - bilateral visual blurring - diplopia - bilateral paresthesia - drop attacks |
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What type of peak systolic velocity (PSV) would you have with 50-79% stenosis? |
PSV greater than 125cm/sec with EDV *less* than 140cm/sec |
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What type of peak systolic velocity (PSV) would you have with 80-99% stenosis? |
PSV greater than 125cm/sec with EDV *greater* than 140cm/sec |
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What range should the doppler angle be at for correct velocity? |
- must be parallel with the artery (45-60 degrees) - heal toe the transducer to obtain desired angle |
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How do you prevent aliasing? |
- change to a lower frequency transducer - decrease the depth of the vessel - increase doppler angle - use a continuous wave |
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Why might you have poor visualization of the carotids? |
- presence of dressings, skin staples or sutures - size and contour of the neck - depth or course of the vessel - patient movement (respiration) - acoustic shadowing from plaque |
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What waveforms should you measure both systolic and diastolic? |
ALL waveforms |
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What is the mean velocity of the doppler signal from the middle cerebral artery (MCA)? |
56cm/sec |
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What happens with antegrade flow of the anterior cerebral resulting from crossover collateralization? |
- flow from the contralateral anterior cerebral via the anterior communicating artery - retrograde flow in the ophthalmic can be from ECA to ICA collateralization |
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What does the right CCA come off of? |
innominate artery |
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What does the left CCA come off of |
directly off the aortic arch |
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Where does the CCA run? |
distally until it reaches the bulb |
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Where is the bulb? |
where the CCA branches into the ICA and ECA |
