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72 Cards in this Set
- Front
- Back
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explain why pressure goes down as velocity goes up?
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PVA=PVA
if the formula starts out as: (3)(2)(4), then area decreases to 1 which causes velocity to increase to 9, this will cause the pressure to go down. |
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what is pressure like distal to a stenosis?
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reduced
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What happens to the sytolic pressure with stenosis? what will the waveform look like as a result of this
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-reduction of systolic pressure
-damped waveform -increased time to peak(acceleration time0 -greater dith of wve at half amplitude |
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differentiate btw stenosis, and critical stenosis?
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stenosis:
-stricture or narrowing of any canal -do not cuase significant reduction in flow volume or pressure distally -CRITICAL STENOSIS: -cause a reduction in volume, pressure and flow(hemodynamically significant) |
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what factors affect the severity of a hemodynamic abnormality?
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-length and diameter of narrowed segment
-rougnmess of endithelial surface -degree of irregularity and shape -ratio of x-sectional area to normal -rate of flow -AV pressure gradient -peripheral resistance beyond stenosis |
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what may increased flow beyond a stenosis suggest?
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collateralization
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steals
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flow from one vascular bed beuing redireted to another
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what are the velocities and flow like within a stenotic region?, what is resitance like proximal to stenotic region?
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high velocities and tubulent flow within stenotic region; high resistant flow approaching stenosis
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what happens to the pulse velocity wave distal to a stenosis? whY?
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ther is damping due to turblence and energy loss.(monophasic doppler sounds)
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what velocities should be taken at the area of stenosis?
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-peak systolic velocity
-eand diastolic velocity -systolic velocity ratio |
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when is the end diastolic velocity normal in regards to a stenosis? when does it change?
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normal if the diameter reduction is <50%
-beyond 50%, diastolic velocity increases in proportion to the narrowing >70%=rapid rise in EDV |
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what factors affect systolic and diastolic velocities?
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-blood pressure, cardiac output, peripheral resitance, collateralization, tandem stenosis, arterial compliance
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what is the point of the ICA/CCA ratio?
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to avoid errors caused by physiologic factors
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how is the ICA/CCA ratio calculated?
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-highest ICA velocity in stenotic segment of ICA/velocity indistal CCA(approx. 2 cm from bif)
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what should be done to "map" a stenosis?
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-visualize plaque
-work sample volume through stenotic region -record and measure highest velocity(take 2-3 samples) -samples and record distal to stenosis to detect turbulence |
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how does diameter reduction compare to area reduction?
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50% DIAMETER REDUCTION=75% area reduction
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diameter reduction
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-compares residual lumen with distal lumen(longitudinal)
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area reduction
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-transverse plane
-percent cross sectional area reduction |
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what are the qualitative factors of doppler waveforms?
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-pulsitility index
-damping factor -inverse damping factor -timing of events |
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pulsitility index
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-applitude of waveform depends on angle btw probe and blood
-amplitude increases as angle approaches 0(parallel) -affects forward and reverse components equally |
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pulsitility index: definition and formula
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-ratio of peak to peak height to mean height-varies from a normal vessel to a diseased one
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how does pulsitility index change as the waveform becomes more damped?
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PI decreases as waveform becomes more damped
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how does the PI increase with a normal patient?
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increases form proximal to distal arteries
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What is the normal pulsitility index of the abdominal AO, CFA, Pop A, and Post tib?
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Abdominal AO-2-6
CFA-5-10 Pop A-6-12 Post Tib-7-15 |
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Damping factor
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measures the degree of attenuation of the doppler signal.
D.F=PI(from proximal sight)/PI (from distal site) |
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inverse damping factor
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-ratio of distal pulstitility index to proximal pulsitility index
-measures the amount of damening of the flow wave as it progresses through an artrial segment I.D.F=Pi(from distal site)/PI(from proximal site) |
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pulse rise time=acceleration time
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delayed rise time is indicitive of proximal disease
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transit time
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-time it takes for doppler signal to travel from one measurement site to another
-inverse of pulse wave velocity pulse wave velocity=1/transit time |
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What is the formula for acceleration time?
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peak velocity/pulse rise time
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deceleration
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rate at which velocity decreases:
peak velocity/pulse decay time |
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frequency spectrum
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rnage of frequencies wthin blood that is extracted using the doppler shift signal
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how is the frequency spectrum determined?
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a spectrum analyzer is used to separated component frequencies.
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how is mean frequency determined(Aka mean velocity)? what is this number used for?
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deermined by taking the area underneath the spectral waveform
-used to calculated the pulsatility index |
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mode frequency
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highest amplitude and brghtest pixel
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median frequency?
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frequency below one half of th total power
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WHAT should be considered when assessing doppler display?
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-presence of flow
-direction of flow -amplitude -window or envelope |
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when can spectral doppler be seen?
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-deceleration of blood
-not centered sample volume-in smaller vessels due to increased parabolic velocity profiles -tortuous vessels(velocity shifts) -turbulent flow -large sample volume -excessive gain/power/dynamic range |
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how do we qualitiatively assess pw doppler?
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-presence or absence of flow
0-direction of flow -phasicity of flow -presence of spectral broadening -strength of doppler signal |
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quantitatibe assessment of spectral display
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-max, mean, and min velocities
-systolic/diastolic ratio -resistive index -pulsitility index -acceleration time and acceleration index |
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what is another name for resistive index?explain resistive index
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pourcelot index:
-max systolic doppler shift minus end diastolic doppler shift divided by max systolic doppler shift |
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explain how the resistive index values work?
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range from 0-1:
1-high resistane values greater than 1 occur with reversed diastolic flow >.7=high <.4=low |
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as pulsitility index increases, what happens to resistnace?
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it increases
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explain pulsitility index? how does it change as it goes down to the feet?
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-max systolic doppler shift-min end diastolic shift/ mean shift
-PI increases as you go down to the feet -considered better parameter because all frequency shifts are considered during a complete cardiac cycle. -higher PI=greater downward resistance -PI>1.2=high; <0.8=low |
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SD ratio
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systolic to diastolic ratio:
Max systolic shift/min end diastolic shift |
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AT
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acceleration time:
-time interval from onset of systole to peak systole -increases downstream to a significant stenosis |
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AI
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acceleration index:
-relationship between systolic up slope to accleration time(rise/run) -cm/s2 -PS velocity/accel time |
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ICA/CCA ratio
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-highest ICA velocity/CCA velocity 2m before bulb(dis)
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what will happen to AT, and AI distal to a high grade stenosis?
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-waveform is damped:
-AT-increased -AI-decreased |
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tardus pardus waveform
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"late and small"
-post stenotic waveform -delayed onset of rounded, poorly defined systolic peak -poor antegrade diastolic flow -small velocities throughout cycle |
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what are the advantages of using color doppler imaging?
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-ability to map flow of large area w/ good spatial res.
-quickly find areas containing blood flow and ab. flow(ie. stenosis and retrograde.) |
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for spectral waveforms, how big should the snamaple volume be, where should the velocity be measured?
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-sample volume as small as possible
-measured at area of max velocity increase |
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what are some things that should be done in order to obtian the best spectral doppler waveform
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-never take waveforms at angles above 60
-sample volume small -sample volume in the center -adjust doppler gain -identify ica and eca -survey entire length -be cautious about SV placement and doppler angle measurements |
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What is the diameter reduction, peak sytolic velicity, and energy, and flow characteristics of an A class stenosis?
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<4KhZ; <125cm/sec
-zero diameter reduction -low spectralbroadening -carotid bulb present -no plaque |
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What is the diameter reduction, peak sytolic velicity, and energy, and flow characteristics of an B class stenosis?
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-1-15%diameter reduction
-<khz; <125cm/sec -min spectral broadening during dec phase -minimal plaque |
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What is the diameter reduction, peak sytolic velicity, and energy, and flow characteristics of an Cclass stenosis?
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-<4khz; ,125cm/s
-16-49% diameter reduction -increased spectral broadening during systole until entire window is filled -plaue visualized in long and short axis |
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What is the diameter reduction, peak sytolic velicity, and energy, and flow characteristics of an D, class stenosis?
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-50-79% diameter reduction
->4khz; >125cm/s -marked spectral broadening is usually associated |
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What is the diameter reduction, peak sytolic velicity, and energy, and flow characteristics of an E class stenosis?
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-total occlusion
-no peak or end diastolic flow or energy -"thump" may be noted at the origin of the stump or occlusion |
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What is the diameter reduction, peak sytolic velicity, and energy, and flow characteristics of anD+ class stenosis?
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80-99% diameter reduction
-end diastolic velocity and energy: >4.5khz; >140cm/sec -marked spectral broadening |
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what happens to create amonophasic sound distal to a proximal significant stenosis?
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low resitance; blood is constantly tryig to get through, and is slowly coming out.
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what happens to create a high pitched, turbulent sound immediately after a tight stenosis?
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high pitched because a fast velocity and turbulent becuase of eddie currents
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what happens to create a systolic thumping proximal to or over a site of complete occlusion?
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blood flow is hitting the stenosis
-can hear it even with trickle flow |
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what happens to create a low pitched, monophasic sound at collateral flow distal to an arterial occlusion?
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-more blood flowing through and being forced flow continuously; softer sound
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what is the sound quality of a normal CCA? Stenotic CCA?
CCA when ICA is occluded? |
norm-prominent systolic sound with flow continuous throughout diastole
-stenotic-turbuletn flow described as "bubble; may be high pitched if significant stenosis -occluded ICA-lower pitch CCA; loss of diastolic component because it is a higher resitant vascular bed |
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what is the sound quality of normal, stenotic, and ica occluded ECa?
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Normal-multiphasic w/ prominent systolic sound and discrete diastolic sound
-stenotic-high pithed turbulent immdiately distal to stenosis -ICA occluded-high pitched with ICA characteristics; if collaterals have developed, a prominent diastolic sound remains |
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Explain normal ICA sound quality, and with severe ICA stenosis, and with ICA occlusion
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NOrm-high pitched and monophasic w/ considerable diastolic flow
-stenosis-very high pitched wi/ marked turbulence -occlusion-no signal |
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be able to draw the doppler signals for sublavian, vertebral, ICA, and ECA
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back of paper w/ heart
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explain the flow of blood n the subclavian and vertebral artery?
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SUBCLAVIAN:
-pulsitile -sharp systolic upstroke and downstroke -flow reversal in diastole -triphasic VERTEBRAL: -low resistance and antegrade flow |
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distinguish btw the different types of quantifying bulb stenosis
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washington/traditional/bulb method-stnosis compared to ECA regular diameter
-NACET, and ACAS-stenotic diameter comared to distal ICA diameter |
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what does ACAS stand for
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assymptomatic
carotid atherosclerotic study |
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what does NACET stand for? what did they figure out70?
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north american symptomatic carotid enartectomy trial:
-wanted to determing how effective endartectomy is -1991-beneficial in >70% stenosis -1998-beneficial in patints w/ 50-69% stenosis |
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what is the NACET criteria?
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>50%-1ca/cca >2
>60%-PSV?260; EDV>70 >70%-ICA/CCA ratio-4; EDV>100 |
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know the chart in diagle pg 55
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do it!
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