Term
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Definition
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Term
| What is the physiological significance of the tissue composition of the aorta? Of the distal arteries? |
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Definition
More elasticity in aorta and proximal arteries. Distal arteries are stiffer (more pulsaltility), have a higher proportion of smooth muscle. (Remember 2 things that help keep diastolic pressure up: 1. Elasticity of the aorta
2. AoV preventing backflow into the heart. |
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Term
| How can the peak pressure be higher at the ankle than in the aorta? |
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Definition
| Pressure increases because of increased stiffness in the tibials(and therefore pulsatility). (Mean pressure is true representation of systemic pressure). |
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Term
| What are approximate mean pressures at each level of the vascular system? |
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Definition
| 15mmHg arteries, 45 mmHg arterioles, 25 mmHg capillaries, 15 mmHg veins |
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Term
| What causes changes in the arteriolar state? |
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Definition
1. Sympathetic nervous system
2. Local chemistry |
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Term
| What is the mechanism of edema formation? What is the significance of plasma proteins? |
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Definition
| Venous hypertension is the most common cause of edema. Too much P in the veins, backing up into the capillaries, interupting the resorption of fluid at the venular end of the capillaries. Plasma proteins drive the osmotic pressure. |
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Term
| How does the venous muscle pump function? |
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Definition
At rest: deep and superficial veins are open and filling with capillary inflow.
With muscular contraction, deep veins are squeezed, moving blood cephalad. Superficial veins are somewhat squeezed as well, moving some blood cephalad. Valves in perforators prevent flow going from deep to superficial.
With relaxation, deep and superficial venous valves prevent backflow (reflux). Negative pressure in deep veins pulls some flow from superficial veins via perforators. |
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Term
| What is the role of soleal sinuses and valves? |
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Definition
| Soleal sinuses= “bellows of the vascular pump.” They gather blood from the soleus muscles. Muscle contraction forces this blood into deeper veins, e.g. popliteal. |
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Term
| What are the main forms of energy in the vascular system and which is by far the predominant form? |
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Definition
| Kinetic energy (energy of motion) and potential energy (stored energy). Potential engery is the large proportion of energy in our body; kinetic energy is just a tiny fraction. |
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Term
| Why is hydrostatic pressure important to the venous system? |
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Definition
| Veins do not have much pressure left in them, so you need another source of energy, the muscle pump aka "the peripheral heart" |
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Term
| What structures prevent hydrostatic pressure from becoming too high (normally)? |
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Definition
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Term
What is Poiseulle's basic flow equation?
the simple resistance equation?
Poiseulle's complicated flow equation?
and the flow equation that gives the continuity equation? |
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Definition
Q=ΔP/R
R=8Lη/πr4
Q= ΔPπr4/8Lη
Q=V•CSA |
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Term
From Poiseulle's complicated flow equation, what is likely to change? What is unlikely to change
[Q= ΔPπr4/8Lη] |
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Definition
| Length and viscosity are unlikely to change; pressure gradient and radius do change appreciably. |
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Term
| Define "laminar" blood flow |
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Definition
| Blood flowing in orderly, undisturbed, concentric layers. |
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Term
| Describe parabolic flow profile |
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Definition
| Velocity is highest in the center, dropping off toward wall. Peak velocity is twice the mean velocity. Velocity at walls is theoretically zero. |
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Term
| Describe plug flow profile |
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Definition
| Velocities are the same almost all the way across the lumen. Wall drag still slows down the outer layers. |
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Term
| What are the two basic velocity profiles? Where and when do they occur? |
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Definition
Plug and parabolic.
Plug profile occurs during acceleration in systole in larger vessles and at stenoses and branches.
Parabolic profile occurs during diastole in larger vessels and throughout the smaller vessles all the time |
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Term
| Why is a peripheral artery Doppler signal triphasic in character; what is really going on inside the lumen? |
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Definition
Foward, reverse, then foward flow components.
Plug profile in early systole. Parabolic in late systole. Reverse flow early Diastole. Less intense forward flow in late Diastole. |
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Term
| What is boundary-layer separation? |
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Definition
| Found at bifurcations (especially pronounced at the carotid bulb). Separated area of flow that swirls around, away from the flow divider. |
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Term
| Where are shear forces higher vs. lower relative to the flow divider of a bifurcation? What are shear forces anyway? |
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Definition
Shear forces are highest at the fastest velocities (against the flow divider). The shear forces are lower at the lower velocities (away from the flow divider). Force acting on a substance in a direction perpendicular to the extension of the
substance. |
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Term
| What is the pathological significance of the lower shear forces in the carotid bulb? |
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Definition
| Plaque tends to form away from the flow divider. Where the shear forces are lower. |
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Term
| What causes phasicity of flow in veins? |
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Definition
| Pressure changes in the thoracic and abdominal cavity due to respiration. |
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Term
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Definition
| The vein’s ability to accommodate more volume with little change in transmural pressure. |
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Term
Where is pulsatile venous flow normal?
Where is it abnormal, and what would it suggest? |
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Definition
Central veins close to the RA.
Bilateral venous pulsatility in the legs would suggest systemic, elevated right heart trouble (e.g. CHF). |
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Term
| What does vasoconstriction do to venous flow? |
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Definition
| This tends to diminish venous flow. This is why we want to have a warm patient when we test…so you have blood to look at! |
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Term
| What equation predicts faster flow through a stenosis? |
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Definition
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Term
| What is a good qualitative definition of arterial stenosis anywhere in the body? |
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Definition
| Focal acceleration with distal turbulence. This is a handy rule of thumb because it tells you that you’re probably going over 50%, even before you get any numbers. |
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Term
Why is energy lost due to stenosis?
How is this energy-loss manifested in an ankle pressure distal to a femoral-artery stenosis? |
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Definition
1) Stenotic turbulence dissipates energy in the form of heat. Also,
2) there’s the change of energy from PE→KE→PE. Whenever there’s a change of energy, you’re losing E in the form of heat.
The pressure is lower distal to the stenosis. Pressure drop between 2 cuffs: this is one way we diagnose LE arterial disease. |
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Term
| Define ischemic vs. hemorrhagic stroke. |
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Definition
Ischemic stroke: occurs when an artery to the brain is blocked.
Hemorrhagic stroke: occurs when a weakened blood vessel ruptures. |
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Term
| Define hemodynamic vs. embolic atherosclerotic lesions. |
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Definition
hemodynamic lesion: is restricting the flow at the site of the plaque.
embolic lesion is throwing “thromboembolic junk” into the cerebral circulation. Embolism= anything traveling in the blood that’s not supposed to be there (blood clot, air bubble). |
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Term
| What are the 4 catagories of plaque? |
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Definition
| 1. Fatty streak 2. Soft plaque (fibrous) 3. Dense plaque (calcific) 4. Heterogeneous plaque (complicated lesion) more dangerous |
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Term
50% by diameter corresponds to what percentage by area?
80% diameter to what percentage by area. |
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Definition
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Term
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Definition
transient ischemic attack
Stoke symptom that is temporary (lasts less than 24 hrs). A warning sign. |
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Term
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Definition
| Cerebrovascular accident. Permanent damage, completed stoke. |
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Term
| What did NASCET and ACAS establish about carotid endarterectomy? |
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Definition
| Established that CEA is recommended to prevent stoke in Pt with >70% stenosis |
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Term
| What is the most common site of lower-extremity stenosis/occlusion? |
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Definition
| SFA, mid to distal thigh (even though it’s not a bifurcation) |
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Term
| What are the stages of symptoms in LE ASO? |
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Definition
1. asymptomatic
2. claudication (consistent if ischemic)
3. rest pain
4. ulceration
5. gangrene |
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Term
| Where does claudication pain usually start first? |
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Definition
| Calves, next big muscle group after the Adductor hiatus. |
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Term
| Where does rest pain usually start? |
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Definition
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Term
| Why might renal artery stenosis or occlusion cause hypertension? |
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Definition
| The kidney is seeing less pressure, and makes the false assumption that systemic pressure is too low, so it cranks out angiotensin and elevates systemic BP. The kidneys are getting bad information if they’re on the other side of a critical stenosis. (Critical stenosis= reduction in P and Q). |
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Term
| What are the 6 stages of the process of plaque formation according to the response-to-injury model? |
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Definition
1. vessel wall injury
2. aggregation of platelets in response to injury
3. platelets generate PDGF= platelet derived growth factor
4. proliferation of smooth muscle tissue
5. connective tissue matrix (scaffold for the plaque tissue)
6. deposition of lipids and other materials (e.g. calcium) into the framework |
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Term
| Where do 90%+ of PE’s come from? |
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Definition
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Term
| How many people die of PE annually in the U.S.? |
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Definition
| ~200,000 (PE gets under-reported. More deaths due to PE than stroke) |
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Term
| Where is DVT thought to begin? |
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Definition
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Term
| What are the primary symptoms of DVT? |
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Definition
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Term
| What are the risk factors for DVT? |
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Definition
1. cancer
2. surgery, especially orthopedic or abdominal
3. bedrest in general
4. pregnancy (oral contraceptives)
5. infection
6. trauma
7. obesity
8. CHF
9. age
10. dehydration |
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Term
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Definition
1. Stasis
2. Hypercoagulability
3. Vessel wall injury |
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Term
| What are the 5 mechanisms that help with venous return to the heart? |
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Definition
1. Venous valves
2. Skeletal muscle pump
3. Respiratory pump
4. Cardiac suction effect
5. Vasomotor tone |
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Term
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Definition
| an abnormal widening or ballooning of a portion of an artery due to weakness in the wall of the blood vessel. Typically involves all 3 layers of the vessel. |
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Term
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Definition
| an abnormal widening or ballooning of a portion of an artery due to weakness in the wall of the blood vessel, however, not involving all 3 layers of the vessel. |
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Term
| Define "dissection" of a vessel. |
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Definition
| interruption in wall, flow underminds and starts "peeling" it away. |
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Term
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Definition
| flow escapes through an interuption in the wall, however, it is contained within the facia of the surrounding muscles or organs and gives an appearance of a aneurysm. |
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Term
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Definition
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Term
What is Raynaud’s syndrome?
Who gets it, usually?
What are some secondary disorders that might cause it? |
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Definition
Abnormal sympathetic response to cold or emotion; triphasic color changes reflecting spasm and recovery: pallor, cyanosis, and rubgor.
Usually young female patients.
Collagen/autoimmune disorder, occupational trauma, frostbite, atherosclerotic obstruction, blood disorder, Thrombo Angiitis Obliterans (TAO) |
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Term
| What is flow character like in an artery proximal to an AV fistula? Why? |
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Definition
| High velocities, especially at diastole because of low resistance. |
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Term
| Who gets Buerger’s disease? |
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Definition
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Term
| What proportion of thoracic outlet syndrome is neurogenic rather than vascular? What are some symptoms? |
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Definition
| Over 90% neurogenic, <10% vascular. Symptoms include weakness, numbness, pain (anything that can either be neurological or ischemic) |
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Term
| What are two components of potential energy that is considered in return blood flow? |
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Definition
| Hydrostatic pressure and gravitational potential energy. |
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Term
| What is hydrostatic pressure? |
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Definition
| Gravity acting on a column of fluid. |
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Term
| What is gravitational potential energy? |
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Definition
| Proportional to height of column of fluid. (Mostly offsets hydrostatic pressure in arterial system--doesn't change driving energy.) |
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Term
What is the Reynold's equation?
What are the factors?
What does a bigger number signify? |
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Definition
Re=Vdρ/η
V=velocity
d=diameter of vessel
ρ=density of fluid
η=viscosity of fluid
The larger the number, the greater the chance of turbulence. |
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