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Terms in this set (85)
Arterial inner layer consists of?
Endothelial cells, connective tissue, elastic layer
Arterial middle layer consists of?
Smooth muscle, elastic, collagen
Arterial outer layer consists of?
Connective tissue, smooth muscle, elastic tissue
Diameter of small & medium arteries
Diameter of arterioles
What alters resistance in arteries?
Circular smooth muscle layer -ex- increased contraction increases resistance
What is the difference between capcitive & compliant?
LOOK THIS UP
Examples of large veins
Portal vein, IVC, SVC, main branches
Size of small & medium veins
Size of venules
Smallest - <20 micrometers
Size of cpaillaries
What does the ICA perfuse?
Anterior & middle portions of brain (gives rise to ophthalic artery
What is the purpose of the Circle of Willis?
Collateral circulation if occulsion
What arteries arise from the ICA?
Anterior communicating, anterior cerebral, & middle cerebral
Describe location of ECA
Medial to ICA & smaller
What is the first branch of the ECA?
What does the ECA perfuse?
Lingual, facial, occipital, posterior auricular, ascending pharyngeal, maxillary, superficial temporal
Describe vertebral arteries
Branch off subclavians, posterior blood supply, join & form Basiliar artery = Circle of Willis
Formula for total fluid energy
Potential energy (intravascular pressure) + kinetic energy
What are 3 types of vascular "energy" losses?
Viscosity, inertia & friction
What is viscosity?
Property that resists fluid to flow
What is inertia?
Occurs when blood is forced to change direction or velocity
What causes most vascular "energy" loss?
What is the difference between veloctiy & blood flow?
-Velocity = distance / time
-Blood flow = volume / time
What drives resistance in arterioles?
What factors increase or reduce resistance to blood flow?
Radius of tube, length of tube & viscosity
Radius & resistance are ___ porportional
Length & resistance are ___ porportional
Viscosity & resistance are ___ porportional
Describe peripheral low resistance
Monophasic (less pulsatile) - forward flow during all phases of cardiac cycle, dilation of arteriolar bed - ICA, vertebral arteries
Describe peripheral high resistance
More pulsatile - antegrade (systole) & retrograde (diastole) flow - vasoconstruction of arteriolar bed - ECA & distal aorta
Describe laminar (layers) flow
Concentric rings of flow through a wide segment of vessel - cells nearest to wall travel slower
Describe parabolic flow
Wider range of velocities - flow through center has highest velocity, more spectral broadening, no spectral window
Describe plug/blunt flow
Flattened velocity profile - cells travel at same velocity, entrance to vessels, early systole, "clean" spectral window
Why isn't Doppler measured at a curve?
Blood moves fast along outer edge of curve
Describe flow in a bulb
Normal - occurs where vessels branch/dilate - blood reverse direction transiently (mostly in systole)
Describe entrance effect
Narrowing - converging flow stabilizes, flattened (plug) profile, clean spectrum occurs at branch points
Describe exit effect
Widening - diverging flow de-stabilizes - disturbed flow, flow separation ICA bulb, aortic aneurysms
Reasons for vascular scans
-ID pts at risk for stroke
-Follow up progression of known disease
-Rule out causes of symptoms
What is pulsatile flow?
-Associated with cardiac cycle (systole - acceleration, diastole - deceleration)
-Cardiac activity = distinct "wave" on Doppler spectrum (waveform = shape)
Describe low pulsatility waveforms
-Broad systolic peaks
-Forward flow systole/diastole (lots of diastolc flow)
-Low peripheral resistance
Describe high pulsatility waveforms
-Tall narrow & sharp systolic peaks
-Reversed/ absent end diastolic flow (diastole)
-High peripheral resistance
How does distal resistance affect pulsatility?
Arteriole walls contract - harder for blood flow though, reduces flow, increases pulsatility, diastolic velocity decreases
Images required for TRANS
CCA, bulb, carotid bifurcation (with & without color)
What should color scale be set to?
Most common place for plaque to develop
Images required SAG
CCA, bulb, prox & distal ICA, prox ECA
Purposes for carotid studies
ID pts at risk for stroke, follow up progression, treatment, R/O causes of symptoms
Common indications of reqs
TIA, stroke, reversible ischemic neurological disorder (RIND), CVA, diplopia, dizziness, headaches, numbness
Purpose of PW Doppler
-Differentiate vessels by analysis of flow patterns
-Listens in detail at a specific sample site (20Hz-20kHz)
-Confirm flow direction of vertebral arteries
Color scale used
If color scale is too low
-Aliasing in normal vessel
-Miss areas of flow disturbance
If color scale is too high
-Low velocity flow missed
Determines if gray-scale/ color image is given more attention
Eliminates low frequency noise
PDI (amplitude mode)
Sensitive to low flow (velocity/direction not assessed)
Directional power Doppler
Shows direction but not velocity (sensitive to lower flow)
Typical scale for PW
Arrhythmias should be assessed with a ___ sweep speed
Which velocity is measured in a arrhytmia?
Most common velocity or several beats
Which velocity is measured in a stenotic region?
Distal venous pressure while standing
Purpose of venous valves
-Prevent retrograde flow
-Ensure efficiency of muscular pump
-Reduce length of blood in column (decrease HP)
Purpose of scanning leg veins
-Diagnose & locate thrombus
-Determine age of thrombus
-Follow natural progression of disease
Drains gastroc muscles into pop
Drains soleus muscles into calf veins
Longest vein in the body and commonly used for grafts
Does the superficial venous system have accompanying arteries?
-Connect deep & superficial veins
-Move blood away from skin
-Can be the cause of venous ulcerations
Venous return mechanisms
-Influence of cardiac activity
Venous flow characteristics
-Phasic d/t respiration & RAP
Ability of blood to accelerate up vein in response to distal manoeurve
Controversy of augment
-Doesn't R/O DVT (partail clot/collateral circulation)
-Doesn't confirm DVT (swollen leg, large pt)
5 characteristics when assessing leg veins with Doppler
4. Doppler signal ceases with Valasalva
5. Unidirectional flow toward heart
Color scale in leg veins
Incidental findings when assessing popliteal fossa
Cysts, hematomas, edema, abscesses, tumors, lymph nodes
Where is atherosclerosis most commonly seen?
Arterial branch points
5 warning signs of stroke
2. Trouble speaking
3. Vision issues
Most common site for plaque
-High lipid content
-Fatty material & Ca+
-May cause attenuation/ shadow
Is calcified plaque a risk for embolizing?
North American Symptomatic Carotid Endarterectomy Trial
"String sign" flow
Shows there's a stenotic lesion distal to waveform
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