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RVT Review > Hemodynamics > Flashcards

Hemodynamics Flashcards

1
Q

Does a damped waveform always indicate a proximal obstruction?

A

No, this could also result from heart condition.

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2
Q

When there is adequate blood flow at rest, but exercise creates a painful lack of blood to the working muscles, this is called:

A

Claudication

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3
Q

What does the spectral display indicate proximal to, within, and distal to a stenosis?

A

Proximal: Increased resistance if no significant collateral, no diastolic flow, increased pulsatility, low velocity.
Stenotic Zone: High velocity, PSV, EDV, and systolic ratios. Spectral broadening, then increased PSV, then increased EDV. May reduce to trickle flow.
Distal: Dampened, slow acceleration time, rounded peak, tardus parvus.

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4
Q

What are the secondary effects of stenosis? (4)

A

Increased velocity (compensatory flow)
Increased volume flow
Reversed flow direction (steals)
Pulsatility changes - i.e. delayed accel. time

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5
Q

What measurements are used to assess a stenosis? (5)

A 
PSV
EDV
Systolic Velocity Ratio
Diastolic Velocity Ratio
Post Stenotic Turbulence
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6
Q

What steps occur in the development of a stenosis, including the effect on the vessel and collaterals?

A

Dilation
Collateral development
Possible steal development
Peripheral dilation of run off bed to reduce resistance

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7
Q

How is a hemodynamically significant stenosis defined?

A

As a drop in both pressure and flow.

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8
Q

Peripheral resistance is primarily controlled by what structures?

A

Pre-capillary sphincter muscles.

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9
Q

What are the three main sources of energy loss in blood vessels?

A

Friction
Inertia
Viscosity

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10
Q

Phasic venous flow results from what action in the body?

A

Respiration

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11
Q

Steady flow may be found in these two parts of the circulatory system:

A

Capillaries (normal steady flow)

Veins (abnormal, indicates partial blockage)

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12
Q

Layered, non-turbulent flow is called:

A

Laminar flow

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13
Q

Laminar flow which has the highest velocity in the center and lower velocity near the wall is called:

A

Parabolic flow

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14
Q

Laminar flow in which the velocity in the center is similar to the velocity near the wall is called:

A

Plug flow

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15
Q

Name two areas where Plug Flow can be found.

A

Aorta

Entrance to stenosis

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16
Q

What is the Reynolds number for turbulent flow?

A

> 2000

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17
Q

What is the cause of phenomena such as murmurs, thrills, and bruits?

A

Turbulent flow

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18
Q

Changes in the direction of flow would result in what kind of energy loss?

A

Inertial energy loss

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19
Q

An increase in hematocrit or a decrease in temperature would increase what kind of energy loss?

A

Viscous energy loss

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20
Q

Energy conversion to heat is due to which type of energy loss?

A

Frictional energy loss

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21
Q

Poiseuille’s Law calculates flow volume based on pressure gradient, vessel radius, vessel length, and fluid viscosity. Which of these variables has the greatest effect on the flow volume?

A

Radius (radius to the fourth power)

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22
Q

In what structures in the cardiovascular system is atherosclerosis most likely to occur?

A

Branch points and bifurcations such as the carotid and aortic bifurcations; and renal, celiac, and other branch points.

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23
Q

Name three areas with a high incidence of atherosclerosis which are not branch points or bifurcations.

A

Hunter’s Canal
Proximal ATA
Distal PTA

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24
Q

The increase in pulse pressure as the pressure wave moves from the heart to the extremities is called:

A

Systolic Amplification

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25
Q

Normal systolic ankle pressure is 10% greater than brachial systolic pressure. What phenomena accounts for this increase?

A

Systolic Amplification

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26
Q

A critical stenosis causes what sort of change to pressure and flow?

A

A hemodynamically significant drop in pressure and flow.

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27
Q

A 50% diameter reduction equates to what percent of area reduction?

A

75%

28
Q

What is the most important factor influencing the severity of an obstruction?

A

The change in diameter.

29
Q

What may develop over time to prevent a loss of total flow to an extremity due to an obstruction?

A

Collaterals

30
Q

Which entrance to a stenosis causes more energy loss, an irregular (asymmetrical) entrance, or a symmetrical entrance?

A

An irregular entrance causes more losses, due to greater friction.

31
Q

Where are energy losses are greater, at the entrance to a stenosis, or at its exit?

A

Exit losses are greater than entrance losses, due to turbulence on the exit side.

32
Q

Which condition would cause greater energy loss, two stenoses in series, or one stenosis as long as the other two combined (assuming all stenoses have the same diameters).

A

Stenoses in series have greater energy losses due to the additive effect of entrance and exit losses.

33
Q

What factors act to compensate for lost flow when plaque is mild to moderate?

A

Vessels expand from increased sheer stress which releases a muscle relaxing factor from the endothelium, leading to vessel expansion.

34
Q

When plaques become severe, what two compensatory mechanisms occur to increase flow to downstream tissues?

A

Development of collaterals

Dilation of capillary beds

35
Q

Collaterals consist of three vessel segments:

A 
Stem arteries (ex. ECA)
Midzone collaterals (ex. facial)
Re-entry vessels (ex. opthalmic)
36
Q

What waveform is seen in a resting patient with PAD/claudication?

A

Monophasic - resistance is low from dilated capillary beds to provide adequate flow at rest.

37
Q

Are patients with rest pain subjected to exercise tests?

A

No need - it would be positive.

38
Q

In a stenosis, Bernoulli’s principle predicts what changes to pressure and velocity?

A

Pressure will decrease while velocity increases. This maintains an equilibrium between kinetic and potential (pressure) energy.

39
Q

List three conditions resulting in distal venous pulsatility.

A

CHF
Fluid Overload
Tricuspid regurgitation

40
Q

Inspiration has what effect on venous return from the lower extremities?

A

Inspiration slows venous return from lower extremities.

41
Q

Inspiration has what effect on venous return from the upper extremities?

A

Inspiration increases venous return from upper extremities.

42
Q

Roughly two-thirds of the total blood volume is found in which vessels: arteries; veins; capillaries?

A

Veins

43
Q

The weight of the uninterrupted column of blood due to gravity is termed ___ pressure.

A

Hydrostatic

44
Q

What structures in the veins prevent retrograde flow and interrupt the column of blood to reduce hydrostatic pressure?

A

Valves

45
Q

List four trophic changes which occur with chronic venous incompetence.

A

Edema
Fibrous deposits
Brawny appearance in gaiter area
Ulceration

46
Q

What must be present for an effective calf veno-motor pump?

A

Working calf muscles
Competent valves
Patent outflow veins

47
Q

Formula for Resistive Index?

A

RI = [1 - (EDV/PSV)] * 100

48
Q

Normal Resistive Index for renal arteries?

A

< 80

49
Q

What problem with cardiac function will be shown in the waveform as a delayed upstroke?

A

Slowed ventricular emptying

50
Q

What problem with cardiac function will be shown in the waveform as reversed diastolic flow?

A

Aortic valve reflux

51
Q

What problem with cardiac function will be shown in the waveform as damping of the pulse?

A

Aortic stenosis

52
Q

What is the effect on resistance, pulsatility and velocity PROXIMAL to a stenosis?

A

Greater resistance and pulsatility, lower velocity.

53
Q

As a vessel narrows over time due to stenosis, what is the effect on the spectral signal, the PSV, and the EDV within the stenotic area?

A

First spectral broadening occurs, followed by increased PSV, and finally increased EDV.

54
Q

Which is the better indicator of severe (70-90%) stenosis, PSV or EDV?

A

EDV.

55
Q

List the five measurements used to assess stenosis.

A 
PSV
EDV
Systolic velocity ratio
Diastolic velocity ratio
Post stenotic turbulance
56
Q

What is the effect on the waveform DISTAL to a stenosis?

A

Damped appearance: slow acceleration time, rounded peak, decreased systolic and increased diastolic velocity. Tardus parvus.

57
Q

List three problems which may trigger a visual bruit.

A

A/V Fistula
Pseudoaneurysm
Significant stenosis

58
Q

When using a headset, which earphone (right or left) provides the forward (antegrade) signals?

A

Right

59
Q

Formula for Pulsatility Index?

A

Peak-to-peak frequency / Mean frequency

60
Q

Which quantitative measure can help differentiate inflow from outflow disease? (Pulsatility index; Inverse damping factor; Acceleration time)

A

Acceleration time

61
Q

How much wider should the pneumatic cuff be than the diameter of the limb on which it is used?

A

At least 20%.

62
Q

For segmental limb pressures, a drop of at least how many mmHg between two consecutive levels is considered significant?

A

> 30mmHg for legs, > 20mmHg arms.

63
Q

A horizontal difference between same segments of legs of how many mmHg suggests obstructive disease in the leg with the lower pressure?

A

20 - 30 mmHg

64
Q

A thigh pressure index of at least what is normal?

A

1.2

65
Q

For healing of foot ulcers, what is the minimum toe pressure needed?

A

At least 30mmHg

RVT Review (5 decks)

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