Term
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Definition
| speed (distance over time) |
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Term
| What are the SI units for velocity? |
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Definition
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Term
| What are the CGS units for velocity? |
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Definition
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Term
| What are the British units for velocity? |
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Definition
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Term
| Which units of velocity are used for echocardiograhy? |
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Definition
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Term
| Which units of velocity are used for vascular? |
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Definition
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Term
| What is the equation that defines the relationship among flow, velocity, and area? |
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Definition
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Term
| If the area of the aorta is 3.3 cm², what is the diameter? (How do you obtain the diameter?) |
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Definition
D = 2√(A/π)
D = 2√(3.3/π)
= 2.05 cm |
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Term
| If the diameter of the aorta is 2.05 cm, what is the area? (How do you obtain the area?) |
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Definition
A = D²•0.785
A = 2.05²•0.785
3.3 cm² |
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Term
| If the velocity is 33 cm/sec, and the flow is 4.4 L/min, what is the diameter of the aorta? (How do you obtain the diameter?) |
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Definition
A=Q/V
First, convert Q to cm³/sec
4.4 L/min(1000/60) = 73.33 cm³/sec
A=73.33/33
A=2.22 cm² |
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Term
| If the area of the aorta is 2.7 cm², and the flow is 5.1 L/min, and the aorta branches in arteries totaling 50 cm², what is the velocity in each branch artery? (How do you obtain the velocity?) |
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Definition
V=Q/Total CSA of branches
First, convert Q to cm³/sec
5.1 L/min(1000/60) = 85 cm³/sec
V=85/50 = 1.7 cm/sec
*The area of the aorta is insignificant information |
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Term
| What is the first branch off the aorta not including the coronary arteries. |
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Definition
| Brachiocephalic (Innominate) Artery |
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Term
| The velocity of blood flow in the LVOT is 88 cm/sec, and the area of the LVOT is 7.7 cm², and the velocity in the aortic valve is 4.4 m/sec. What is the valve area? (How do you obtain the area?) |
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Definition
V1A1=V2A2
in this case:
(V1A1)/V2
But first convert V2 to cm/sec:
4.4 m/sec • 100 = 440 cm/sec
A2 = (88•7.7)/440 = 1.54 cm2
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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
| 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
| 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
| Define "turbulence" and what noises might it cause in the body? |
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Definition
| Chaotic and disorderly flow. In cardiac studies, turbulence is called a "murmur" and called a "brooie" in vascular studies. |
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Term
| What are the variables that influence the likelihood of turbulence? |
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Definition
| If V=velocity, d=diameter or ρ=density is increased, or η=viscosity is decreased, the likelihood of turbulence will increase. |
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Term
| Give the equation that predicts the likelihood of turbulence and who developed it? |
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Definition
The Reynolds number equation:
Re=Vρd/η
V=velocity, d=diameter, ρ=density, η=viscosity
A Reynolds number >2000 predicts turbulence |
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Term
| What is the effect on the likelihood of turbulence with a tripling of viscosity? |
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Definition
| The likelihood of turbulence will decrease 1/3. |
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Term
| When might a cardiac murmur be normal? |
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Definition
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Term
| When is a cardiac murmur never normal? |
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Definition
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Term
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Definition
| An internal friction created by molecular attraction, creating a tendency to resist motion. |
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Term
| What degree of stenosis must be reached in most arteries to be critical? |
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Definition
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Term
| How is "critial stenosis" defined? |
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Definition
| A sudden reduction in flow and blood pressure. |
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Term
| What is the the behavior of blood flow before, within, and distal to the hemodynamically significant stenosis? |
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Definition
| There is no noticable change in blood flow, but within the stenosis, the velocity increase due to the narrowing of the vessel. Once the flow is distal to the stenosis, turbulence ensues. |
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Term
| What happens to pressure within a stenosis and why? |
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Definition
| There is a reduction in pressure due to the Bernoulli effect which states, "As the speed of a moving fluid increases, the pressure within the fluid decreases." |
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Term
| If velocity through a mitral valve is 410 cm/sec, what is the pressure gradient across the valve? |
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Definition
P1-P2 = 4(V2)
First, convert cm to m
410 cm/sec • 100 = 4.1 m/sec
ΔP = 4(4.12) = 67 mmHg |
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Term
| What is the most common complication resulting from atherosclerotic diease in the coronary arteries? |
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Definition
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Term
| What is the most common complication resulting from atherosclerotic diease in the carotid arteries? |
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Definition
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Term
| What is almost always the first symptom of lower extremity PAD? |
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Definition
| Pain with exercise, relief with rest. |
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Term
| What is an aneurysm and possible causes? |
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Definition
| Weakening and bulging of the cardiac or arterial wall. Can be due to infarcted tissue, atherosclerotic degeneration, infection, or congenital weakness. |
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Term
| What is the formula for the Law of LaPlace? Define the variables. Explain its significance in the vascular system. |
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Definition
T∝P•d
Wall tention (T) is proportional to (∝) pressure (P) multiplied by diameter(d). The larger the vessel's diameter, the more tension is required to sustain a given pressure. In the body, the mean pressure doesn't change much--it's the diameter that changes as the wall weakens, requiring more wall tension to hold things together. |
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Term
| What are the units for wall tention? |
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Definition
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Term
| What happens to wall tension if the diameter is tripled? |
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Definition
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Term
| What is usually found on the wall of an aneurysm? |
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Definition
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Term
| What are the two basic functions of the venous part of the circulatory system? |
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Definition
| To return blood back to the heart and venous resevior. |
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Term
| What are the two possible useful functions of the venous reservor? |
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Definition
| To provide increased flow during exercise and provide volume to the core circulation in the event of severe hemorrhage. |
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Term
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Definition
| The ability to expand and contgain more volume with little pressure increase. |
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Term
| What makes veins compliant? |
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Definition
| Veins are compliant because of normally semi-collapsed state. |
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Term
| What makes arteries compliant? |
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Definition
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Term
| What are the physical characteristics of veins compared to arteries. |
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Definition
| Roughly half the wall thickness than arteries. Veins contain less elastin and smooth muscle in the media comparted to arteries. |
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Term
| Define "hydrostatic pressure" |
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Definition
| Force of gravity acting on a column of fluid. |
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Term
| How much hydrostatic pressure is possible in an average person standing still for a long time? |
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Definition
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Term
| What structures help prevent hydrostatic pressure from happening? |
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Definition
| Venous valves and calf muscle. |
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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
| What are the 3 types of venous structures in the lower extremities, and how do they function? |
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Definition
| Flow moves from (1) superficial veins to (2) deep veins via (3) perforating veins. |
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Term
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Definition
1. Stasis
2. Hypercoagulability
3. Vessel wall injury |
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Term
| How is LE DVT thought to form? |
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Definition
DVT is thought to originate often in two places from stasis:
1. Muscular veins in calf
2. Behind valve leaflets |
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Term
| What is the most serious complication of DVT? |
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Definition
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Term
| What are the two basic types of testing for DVT? |
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Definition
1. Venous outflow plethysmography
2. Ultrasound |
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Term
| How is venous imaging performed? |
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Definition
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Term
| What demostrates patency of the vein? |
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Definition
| Compress veins with ultrasound probe to provoke reflux. |
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Term
| What image characteristics are present for acute thrombus? |
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Definition
1. Dark intraluminal echoes
2. Homogeneous echoes
3. Distension of vein
4. Poor wall attachment ("tail") |
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Term
| What image characteristics are present for chronic thrombus? |
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Definition
1. Bright intraluminal echoes
2. Heterogeneous echoes
3. Possible retracted, small lumen
4. Well attached to wall
5. May see recanalization collaterals
6. Vein may be invisible |
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Term
| How is Doppler ultrasoundused to diagnose venous valvular insuffciency? |
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Definition
| flow direction, proximal compression, distal release. |
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