Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
101 Cards in this Set
- Front
- Back
|
what 2 factors control peripheral vascular resistance?
|
autoregulation
sympathetic nerve innervations |
|
|
resistance formula
|
R=8LN/piertothe 4th.
|
|
|
as pressure increases, what happens to resistance in a vessel?
|
pressure causes the vessel to dialate, so resistance is deceased
|
|
|
hydrostatic pressure
|
p=mgh
|
|
|
how is viscocity related to hematocrit?
|
the higher the hematocrit, the higher the viscocity
|
|
|
what is the formula for flow?
|
velocity x cross sectional area
|
|
|
what factors affect the arterial pressure wave?
|
stroke volume
time of ventricular ejection peripheral resistance compliance or stiffmess |
|
|
what happens to resistance with small diameter changes
|
large resistance changes
|
|
|
what is the formula for poisoilles law?
|
4piertothe4th(change in pressure)/8Ln
|
|
|
what is turbulent flow directly and inversly proportional to?
|
directly:
-velocity -density -diameter of vessel inversely=viscocity |
|
|
what are the 2 periods of increased venous flow during each cardiac cycle?
|
-v-wave
-after c-wave |
|
|
what parameters increase the amount of energy lost to heat?
|
-increased velocity
-increased viscocity -rougher surface -small cross sectional area |
|
|
what happens when there is a high transmural pressure?
|
the vein distends
|
|
|
what is the windkessel effect?
|
-when fluid is forced into a complieant vessel causing it to expand and increase the volume within it. Later, when pressure is reduced, vessel contracts, producing extended flow.
|
|
|
what are the consequences of a dissection and possible ultrasound findings?
|
CONSEQUENCES:
-embolism -flow disturbances -pseudoanyrsm U/S findings: -flow reversal -intimal flap -narrowing of ICA w/out visible plaque |
|
|
neointimal hyperplasia
|
-growth of cells post endartectomy
-post vein bypass graft=narrowing or occlusion |
|
|
stents
|
2 types:
1)self expanding 2)deploy balloon in angioplasty |
|
|
subclavian steal syndrome
|
-proximal subclavian occlusion
-flow reversal in ipsilateral vvertebral artery -may result in neurological symptoms when significant ICA disease exists |
|
|
what does fibromuscular dysplasia look like sonographically?
|
string of pearls found in carotid and renal arteries
|
|
|
name some specific arteritis/vasculitis important to vascular sonography
|
-berger's syndrome-constriction of peripheral vessels
-giant cell arteritis-occurs in elderly -takayasu's arteritis-young asian women |
|
|
angioplasty
|
balloon tipped catheter is inflated and crushes plaque and opens up vessel
|
|
|
VBI; what are the symptoms?
|
verebrobasilar insufficiency; symptoms include:
-ataxia(uncoordination) -limb weakness -paresthesia -vertigo -diplopia |
|
|
digital substraction arteriography
|
a technique for digital storage, subtraction and enhancement of fluoroscopically generated x-ray images
-permits the use of much smaller concentrations of contast material to e used |
|
|
what is a tardus parvus waveform?
|
-damped flow
-delay onset(rounded systolic peak) -poor antegrade flow -decreased velocities -most frequent in renal arteries |
|
|
what are bruit's related to?
|
-post stenotic turbulence
-av fistula -transmitted cardiac murmur |
|
|
what are the classifications of arteritis/vasculitis?
|
primary or secondary to drug toxin and infection
|
|
|
what type of disease is fibromuscular dysplasia? what is it
|
non-atherosclerotic disease
-dysplasia of the media -presents in 25-50 yrs -1male:3 females have this -may present as TIA or thromboembolic stroke -more common in renal arteries -associated w/intracranial aneurysms |
|
|
symptoms of TIA and RIND
|
SYMPTOMS:
-Monocular blindness(amaurosis fugax) -dysphasia/aphasia of communication -contralateral hemiparesis -behavioral disturbances |
|
|
What is seen with ASO(atheroscloerosis obliterans)?
|
-endothelial injury
-lipoprotien deposit -inflammatory response -thickening, hardening, and loss of elasticity of arterial walls. |
|
|
how does venous blood flow to the heart?
|
semilunar valves in the deep and superficial systems and calf muscle veins allow blood to proceded in one direction;
-vales in the perforator veins allow blood flow in one direction, from superficial to deep veins. |
|
|
what venous valves open and close during relaxation?
|
proximal valves close due to hydrostatic pressure, and distal ad perforator valves open to allow blood to fill the empty venous segments
|
|
|
what is pulse pressure amplitude? explain it?
|
pulse pressure amplitude-the difference btw systolic and diastolic pressure
-is affected by SV, time of ventricular ejection, resistance, and stiffness of walls |
|
|
what is hydrostatic pressure?
|
pressure created by the weight of a volume of blood.
|
|
|
what is secondary venous incompotence?
|
valve damage due to dvt
|
|
|
how do you determine percent diameter reduction?
|
measure the true diameter of the artery and then the resudual lumen and apply the following formula:
%D stenosis=1-(TLdivided by RL)x100 |
|
|
how does flow change btw systole and diastole?
|
there is plug flow in systole, and parabolic flow in diastole
|
|
|
what can an increase in hydrostatic pressure cause?
|
-high trasmural pressures
-venous distention distally -filtration of fluids into extracellular spaces -reduced venous return |
|
|
what 3 factors are required for efficient pump action?
|
-musles in limbs must be able to contract and compress veins
-valves must operate correctly -venous outflow ust be unobstructed. |
|
|
what is the formula for reynalds number?
|
re=vq2r/n
|
|
|
what may happen to blood flow in arterial occlusive disease?
|
blood flow may increase in blanches of the arterial system to compensate for decreased blood flow in the diseased artery
|
|
|
what can chronic venous edema result in?
|
stasis dermatitis and ulceration
|
|
|
what do hemodynamic abnormalities depend on?
|
length and diameter of narrow segment
-rouhness of endothelial surface -irregularity of narrowing -rate of flow -arterio-venous PG -peripheral resistance |
|
|
what are the primary complications of hemodyalysis grafts and fistulas?
|
stenosis
-occlusion -pseudo-aneurysm -arterial steal sydrome from distal perfusion |
|
|
why might a normally triphasic waveform appear biphasic?
|
if the patient recently exercised, the reversal component would be absent due to a decrease in peripheral resistance
|
|
|
FFT
|
analysis of returing doppler signal and displays the frequency shifts on a spectral display.
-breaks down complex signals into each individual frequency groups and assigns them to bins. -vertical axis represents frequecy shift -horizontal axis resprests time |
|
|
autocorrilation
|
info from multiple pulses along one line is compared to preceding puse echo
-at least 3 pulses per scan line are required for autocorrelation -scan lines are processed to generate a frame of color doppler info based on frequency shifts occuring along each scan line |
|
|
power doppler
|
analysis of returing doppler signal and displays the frequency shifts on a spectral display.
-may velocities and frequecy shifts are represented -breaks down complex signals into each individual frequency groups and assigns them to bins. -vertical axis represents frequecy shift -horizontal axis resprests time |
|
|
explain bins in FFT?
|
They are like musical chords; the FFT helps determine which notes make up that chord or which individual frequencies comrise the doppler signal
|
|
|
how do we minimize aliasing?
|
-increse PRF(scale)
-adjust baseline -increase dopler angle of incidence to lower frequency shift -use lower frequency transduer to lower frquency shift -use a continuouse wave transducer |
|
|
analog doppler waveform generation
|
-uses a simple method called zero crossing detection
-the number of times it crosses per time interval is the zero crossing frequency -does not display true peak frequencies |
|
|
explain the procees of extracting the doppler signal
|
-signal is weak compared to echos from tissue, so the signal is amplified and processed(domodulated)by the doppler system.
-sent to speakers -processes in an analog to digital converter, and stored in memory -digital signal sent for FFT analysis |
|
|
what does autocorrilation provide?
|
-flow direction
0average or mean frequency shift -pwer or amlitude -varience |
|
|
caplillaries
|
4-10mu meters
-permit exchange of nutrients and wastes btw blood ans intersitial fluid |
|
|
what is the cosine of 30, 40, and 50 degrees?
|
30-.87
40-.77 50-.64 |
|
|
tardus parvus waveform
|
"late and small"
-post stenotic waveform -delayed onset of rounded, poorly defined systolic peak -poor antegrade diastolic flow -small velocities throughout cycle |
|
|
how is angle affected w/ pulsitility index?
|
amplitude increases as angle approaches 0(parallel)
-affects forward and reverse components equally |
|
|
what is a delayed rise time indicitivev of? what does pulse rise time equal?
|
indicitive of proximal disease
-pulse rise time=acceleration time |
|
|
what are the qualitative factors of doppler waveforms?
|
-pulsitility index
-damping factor -inverse damping factor -timing of events |
|
|
AT
|
acceleration time:
-time interval from onset of systole to peak systole -increases downstream to a significant stenosis |
|
|
diameter reduction vs. area reduction?
|
50% DIAMETER REDUCTION=75% area reduction
|
|
|
frequency spectrum
|
rnage of frequencies wthin blood that is extracted using the doppler shift signal
|
|
|
explain resistive index values
|
range from 0-1:
1-high resistane values greater than 1 occur with reversed diastolic flow >.7=high <.4=low |
|
|
what is another name for resistive index? explain?
|
pourcelot index:
-max systolic doppler shift minus end diastolic doppler shift divided by max systolic doppler shift |
|
|
distinguish btw the different types of quantifying bulb stenosis
|
washington/traditional/bulb method-stnosis compared to ECA regular diameter
-NACET, and ACAS-stenotic diameter comared to distal ICA diameter |
|
|
pulsitility index: definition and formula
|
-ratio of peak to peak height to mean height-varies from a normal vessel to a diseased one
-PI>1.2=high; <0.8=low -max systolic doppler shift-min end diastolic shift/ mean shift |
|
|
how do we qualitiatively assess pw doppler?
|
-presence or absence of flow
0-direction of flow -phasicity of flow -presence of spectral broadening -strength of doppler signal |
|
|
median frequency
|
frequency below one half of th total power
|
|
|
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 |
|
|
damping factor
|
measures the degree of attenuation of the doppler signal.
D.F=PI(from proximal sight)/PI (from distal site) |
|
|
nacet criteria
|
>50%-1ca/cca >2
>60%-PSV?260; EDV>70 >70%-ICA/CCA ratio-4; EDV>100 |
|
|
diameter reduction
|
-compares residual lumen with distal lumen(longitudinal)
|
|
|
transit time
|
-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 |
|
|
rete mirabelle
|
(wonderful net)
-consists of a network of trnasdural arteries which may anastamose across the subdural space within the tiny arteries covering the surface of the brain |
|
|
vertebral veins
|
course through the transvers processes of the cervical vertebrae adjacent to arterial counterparts.
-empty into subclavian vein before joining w/IJV |
|
|
what is the first branch to arise from the aortic arch?
|
brachocephalic/innominate-behind the junction of teh clavicle and sternum
-branches into the Rt sublavian and rt common carotid |
|
|
cerebellum
|
-aids in coordination of volumtary muscles
-maitains balance -maintains muscle tone |
|
|
vertebral dissections
|
-more common in young people
-spontaneous or related to injury-susceptible to injury at top of jeck -can result in stroke |
|
|
what suggests subclavian stenoss?
|
-20mmhg PG btw Lt and Rt brachial pressures
|
|
|
to/fro pattern
|
-results from increasesing subclavian stenosis
-retrograde flow in systole -antegrade flow in diastole -brachial pressure gradient |
|
|
what are some causes of subclavian steel syndrome?
|
-atherosclerotic disese
-trauma -embolus -surgical complications -congenital cuses -neoplastic factors |
|
|
what branches of the ICA leave the intracranial space?
|
-fronatal
-supraorbital -nasal artery |
|
|
what is the second most NB source of collateral flow to the brain?
|
-anastomosis btw branches of teh ECA and ICA via the orbital and opthalmic arteries.
|
|
|
what are some features of the vertebral artery?
|
-enter the foramina transversaria of the sixth cervical vertebrae
-leave at the atlanto-occipital interspace and loop anterior to enter foramen magnum -unite at pontomedullary junction to for basilar artery |
|
|
what are some cuases of VBI?
|
-atherosclerosis of small branches
-embolization -carotid and vertebral occlusive disease -ectasia -dysrrythmias -steal syndroms -impingement -dissection |
|
|
what are some reasons for an elevated vertebral artery velocity?
|
-dominent compensory vertebral artery
-compensory mechanism for occlusive disease -anatomically small -extrinsic compression from spine -midvertebral atherosclerotic stenosis-rare |
|
|
what are the major ECA branches?
|
-superior thyroid
-lingual facial -ascending pharyngeal -external and internal maxillary -transverse facial -occipital -posterior aurical -superficial temporal arteries |
|
|
occipital lobe
|
contains visual association area
|
|
|
what is teh first branch of the ICA and the first branch of the ECA?
|
ICA-opthalmic artery
ECA-supertior thyroid |
|
|
which ECA collaterals can communicate w/ the opthalmic artery?
|
-occupital
-facial -superficial temporal -internal maxillary arteries |
|
|
where do VBI symptoms occur?
|
-usually bilateral symptoms because the post. brain doesn't have 2 lobes like the anterior portion.
|
|
|
explain the waveforms of severe to mild subclavian steel syndrome?
|
-complete subclavian steel-blood comes up and goes cross and down contralateral vertebral artery
-incomplete or partial steal-transient reversal of vertebral flow; may be converted into complete steal using provocative mesures -presteal or "bunny" waveform -tradus parvis waveform |
|
|
medulla oblongota
|
-regulates muscles of resipiration
-rate and force of hearbeat -contraction of smooth muscles in blood vessel walls |
|
|
brain stem
|
-midbrain, pons, medulla oblongota
-relaycenter for eye and ear -connects nerve impulses from cerebellum |
|
|
when is resistive flow seen in vertebral arteries?
|
-distal obstruction in vertebral arteries
-distal obstruction basilar arteries -dissection |
|
|
ICA
|
-supplies anterior brain circulation
-larger and more lateral than ECA -four segments: -cervical-straight -petrous-canal through petrous bone -cavernous-gives rise to first branch of ICA(opthlmic artery) -supraclinoud-where ICA becomes anterior cerebral artery |
|
|
what are the 3 major collateral routes?
|
-the other side of the circle of willis
-posterior cerebral circulation -ECA branches |
|
|
what is damping factor measureing/
|
the degree of attenuation of the doppler signal
|
|
|
incomplete SSS
|
obstruction doesn't cause complete flow reversal:
-causes systolic flow deceleration which(if severe) may manifest as bidirectional flow |
|
|
if there is a decreased pulsitility index, what happens to the severity of arterial occlusive disease?
|
it becomes more severe
|
|
|
zero-crossing detector
|
-used for generating an analog waveform on a strip chart recorder for qualitative assessment
-dependant on signal to noise ratio and amplitude |
|
|
How are NACET and ACAS different from the washington/bulb/traditional method of measureing stenosis?
|
NACET/ACAS-compare the disease free ICA lumen to the residual lumen
WASHINGTON/TRADITIONAL/BULB-compare diameter of residual lumen at the narrowestpoint: ICA bulb diameter. |
