Hemodynamics

Question 1

Does a damped waveform always indicate a proximal obstruction?

Answer 1

No, this could also result from heart condition.

Question 2

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

Answer 2

Claudication

Question 3

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

Answer 3

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.

Question 4

What are the secondary effects of stenosis? (4)

Answer 4

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

Question 5

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

Answer 5

PSV
EDV
Systolic Velocity Ratio
Diastolic Velocity Ratio
Post Stenotic Turbulence

Question 6

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

Answer 6

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

Question 7

How is a hemodynamically significant stenosis defined?

Answer 7

As a drop in both pressure and flow.

Question 8

Peripheral resistance is primarily controlled by what structures?

Answer 8

Pre-capillary sphincter muscles.

Question 9

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

Answer 9

Friction
Inertia
Viscosity

Question 10

Phasic venous flow results from what action in the body?

Answer 10

Respiration

Question 11

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

Answer 11

Capillaries (normal steady flow)

Veins (abnormal, indicates partial blockage)

Question 12

Layered, non-turbulent flow is called:

Answer 12

Laminar flow

Question 13

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

Answer 13

Parabolic flow

Question 14

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

Answer 14

Plug flow

Question 15

Name two areas where Plug Flow can be found.

Answer 15

Aorta

Entrance to stenosis

Question 16

What is the Reynolds number for turbulent flow?

Answer 16

> 2000

Question 17

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

Answer 17

Turbulent flow

Question 18

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

Answer 18

Inertial energy loss

Question 19

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

Answer 19

Viscous energy loss

Question 20

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

Answer 20

Frictional energy loss

Question 21

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?

Answer 21

Radius (radius to the fourth power)

Question 22

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

Answer 22

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

Question 23

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

Answer 23

Hunter’s Canal
Proximal ATA
Distal PTA

Question 24

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

Answer 24

Systolic Amplification

Question 25

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

Answer 25

Systolic Amplification

Question 26

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

Answer 26

A hemodynamically significant drop in pressure and flow.

Question 27

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

Answer 27

75%

Question 28

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

Answer 28

The change in diameter.

Question 29

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

Answer 29

Collaterals

Question 30

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

Answer 30

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

Question 31

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

Answer 31

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

Question 32

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).

Answer 32

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

Question 33

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

Answer 33

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

Question 34

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

Answer 34

Development of collaterals | Dilation of capillary beds

Question 35

Collaterals consist of three vessel segments:

Answer 35

``` Stem arteries (ex. ECA) Midzone collaterals (ex. facial) Re-entry vessels (ex. opthalmic) ```

Question 36

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

Answer 36

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

Question 37

Are patients with rest pain subjected to exercise tests?

Answer 37

No need - it would be positive.

Question 38

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

Answer 38

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

Question 39

List three conditions resulting in distal venous pulsatility.

Answer 39

CHF Fluid Overload Tricuspid regurgitation

Question 40

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

Answer 40

Inspiration slows venous return from lower extremities.

Question 41

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

Answer 41

Inspiration increases venous return from upper extremities.

Question 42

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

Answer 42

Veins

Question 43

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

Answer 43

Hydrostatic

Question 44

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

Answer 44

Valves

Question 45

List four trophic changes which occur with chronic venous incompetence.

Answer 45

Edema Fibrous deposits Brawny appearance in gaiter area Ulceration

Question 46

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

Answer 46

Working calf muscles Competent valves Patent outflow veins

Question 47

Formula for Resistive Index?

Answer 47

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

Question 48

Normal Resistive Index for renal arteries?

Answer 48

< 80

Question 49

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

Answer 49

Slowed ventricular emptying

Question 50

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

Answer 50

Aortic valve reflux

Question 51

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

Answer 51

Aortic stenosis

Question 52

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

Answer 52

Greater resistance and pulsatility, lower velocity.

Question 53

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?

Answer 53

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

Question 54

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

Answer 54

EDV.

Question 55

List the five measurements used to assess stenosis.

Answer 55

``` PSV EDV Systolic velocity ratio Diastolic velocity ratio Post stenotic turbulance ```

Question 56

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

Answer 56

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

Question 57

List three problems which may trigger a visual bruit.

Answer 57

A/V Fistula Pseudoaneurysm Significant stenosis

Question 58

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

Answer 58

Right

Question 59

Formula for Pulsatility Index?

Answer 59

Peak-to-peak frequency / Mean frequency

Question 60

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

Answer 60

Acceleration time

Question 61

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

Answer 61

At least 20%.

Question 62

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

Answer 62

>30mmHg for legs, > 20mmHg arms.

Question 63

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

Answer 63

20 - 30 mmHg

Question 64

A thigh pressure index of at least what is normal?

Answer 64

1.2

Question 65

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

Answer 65

At least 30mmHg