Vascular Ultrasound UPDATED Exam
Questions and CORRECT Answers
What are the two types of energy that exist in the circulation? Example of each - CORRECT
ANSWER - Potential energy = pressure in the vessels
Kinetic energy = velocity of blood flow
Describe the energy transfer between potential and kinetic energy using Bernoulli's equation -
CORRECT ANSWER - When the lumen increases, kinetic energy (blood flow) is
converted back to potential energy (pressure)
vice versa
What kind of pressure is located in the lower extremities and is used to equalize pressure to the
level of the heart? - CORRECT ANSWER - Hydrostatic pressure
What is laminar flow? - CORRECT ANSWER - flow is faster at the center of the vessel
than at the outside due to friction of the endothelial layer
Poiseuille's law states: - CORRECT ANSWER - Q = [ π * (P1 - P2) * r4 ] / 8Lη:
states that in a cylindrical tube, the mean velocity of laminar flow is directly proportional to the
pressure differences from the start to the end of the tube and the square of the radius, while being
inversely proportional to the length of the tube and the viscosity of the fluid
Poiseuille's Law:
Small changes in the _______ may result in large changes in ________ _______ - CORRECT
ANSWER - radius
volume flow
What are the factors for varying degrees of deviation from laminar flow? (2) - CORRECT
ANSWER - 1. Blood flow velocity changes
2. Diameter changes (alter lines of flow)
,Laminar flow can be altered at ________, ____________, ________ and __________
__________ - CORRECT ANSWER - curves, bifurcations, branches and stenotic lesions
The development of turbulence depends mainly on what? (2) - CORRECT ANSWER - 1.
size of the vessel
2. velocity of blood flow
Mild turbulence is likely to occur when? (3) - CORRECT ANSWER - 1. body movements
2. changes in vessel dimensions
3. roughness of endothelial surface
Severe turbulence is likely to occur when? (4) - CORRECT ANSWER - 1. high flow
2. stenosis
3. decreased diameter
4. high pressure to low pressure areas
The heart maintains a _______ volume of blood and pressure at the arterial end of the
circulation. - CORRECT ANSWER - high
What factors have a role in the amplitude and shape of an arterial pressure wave? (4) -
CORRECT ANSWER - 1. stroke volume
2. timing of ventricular ejection
3. peripheral resistance
4. stiffness of arterial walls
An increase in the factors influencing amplitude and shape of arterial pressure wave will do
what? - CORRECT ANSWER - increase the pulse amplitude and in some cases the
systolic pressure.
,What does arterial stiffness mean? When do arteries stiffen? - CORRECT ANSWER -
refers to the elastic modulus of the wall material.
arteries stiffen towards the periphery and as you age
Describe pressure changes which occur throughout the circulation (4) - CORRECT
ANSWER - 1. Pressure begins high in the arteries; little resistance
2. Decreases slightly between aorta and arteries
3. Pressure decreases across the arterioles and capillaries; but resistance increases significantly
4. Pressure continues to drop in the veins; resistance decreases dramatically as well
Pulsatile changes in minute arteries, arterioles, and capillaries are reduced by
________________ and enhanced by ______________ - CORRECT ANSWER -
vasoconstriction
vasodilation
Pulsatile changes in small and medium arteries are reduced by _________________ and
increased by ______________ - CORRECT ANSWER - vasodilation
vasoconstriction
How does temporary cessation of forward flow or flow reversal occur? - CORRECT
ANSWER - A negative gradient is created after a wave has passed through one vessel but
is still traveling through a more distal one during the diastolic period of the cardiac cycle.
Flow reversal is generally only seen in which arteries? - CORRECT ANSWER - high
resistance (lower extremity) arteries
List the factors determining severity of a stenosis (7) - CORRECT ANSWER - 1. length
and diameter of the narrowed segment
2. roughness of the endothelial surface
3. degree of narrowing (abrupt or gradual)
4. ratio of cross-sectional area of narrowed segment to normal segment
, 5. rate of flow
6. arteriovenous pressure gradient
7. peripheral resistance beyond stenosis
Why is there more energy loss from tandem lesions than solitary stenosis? - CORRECT
ANSWER - there is a large loss of energy from disturbed flow patterns (jet effects,
turbulence, eddys)
more entrances and exits to lose energy at
Describe changes that may be seen in the pressure waveform distal to a stenosis (5) - CORRECT
ANSWER - 1. decrease in systolic pressure
2. decrease in amplitude of pressure wave distal to stenosis
3. dampening of pressure waveform
4. increased time to peak
5. greater width of pressure wave
What happens to the pressure waveform distal to a stenosis when blood flow is enhanced through
exercise or hyperaemia testing? - CORRECT ANSWER - The detectable decrease is
accentuated:
Enhanced blood flow through the stenosis will result in an increased loss of energy from friction
and velocity.
True or False?
At rest, it is possible to have normal blood flow in the presence of a severe stenosis or complete
obstruction - CORRECT ANSWER - True, the overcompensation by the cardiovascular
system is not sufficient to pass the occlusion and the flow can appear normal
You will only really see changes in blood flow at rest when? - CORRECT ANSWER - If
the occlusion is acute or there are more than one in series
Questions and CORRECT Answers
What are the two types of energy that exist in the circulation? Example of each - CORRECT
ANSWER - Potential energy = pressure in the vessels
Kinetic energy = velocity of blood flow
Describe the energy transfer between potential and kinetic energy using Bernoulli's equation -
CORRECT ANSWER - When the lumen increases, kinetic energy (blood flow) is
converted back to potential energy (pressure)
vice versa
What kind of pressure is located in the lower extremities and is used to equalize pressure to the
level of the heart? - CORRECT ANSWER - Hydrostatic pressure
What is laminar flow? - CORRECT ANSWER - flow is faster at the center of the vessel
than at the outside due to friction of the endothelial layer
Poiseuille's law states: - CORRECT ANSWER - Q = [ π * (P1 - P2) * r4 ] / 8Lη:
states that in a cylindrical tube, the mean velocity of laminar flow is directly proportional to the
pressure differences from the start to the end of the tube and the square of the radius, while being
inversely proportional to the length of the tube and the viscosity of the fluid
Poiseuille's Law:
Small changes in the _______ may result in large changes in ________ _______ - CORRECT
ANSWER - radius
volume flow
What are the factors for varying degrees of deviation from laminar flow? (2) - CORRECT
ANSWER - 1. Blood flow velocity changes
2. Diameter changes (alter lines of flow)
,Laminar flow can be altered at ________, ____________, ________ and __________
__________ - CORRECT ANSWER - curves, bifurcations, branches and stenotic lesions
The development of turbulence depends mainly on what? (2) - CORRECT ANSWER - 1.
size of the vessel
2. velocity of blood flow
Mild turbulence is likely to occur when? (3) - CORRECT ANSWER - 1. body movements
2. changes in vessel dimensions
3. roughness of endothelial surface
Severe turbulence is likely to occur when? (4) - CORRECT ANSWER - 1. high flow
2. stenosis
3. decreased diameter
4. high pressure to low pressure areas
The heart maintains a _______ volume of blood and pressure at the arterial end of the
circulation. - CORRECT ANSWER - high
What factors have a role in the amplitude and shape of an arterial pressure wave? (4) -
CORRECT ANSWER - 1. stroke volume
2. timing of ventricular ejection
3. peripheral resistance
4. stiffness of arterial walls
An increase in the factors influencing amplitude and shape of arterial pressure wave will do
what? - CORRECT ANSWER - increase the pulse amplitude and in some cases the
systolic pressure.
,What does arterial stiffness mean? When do arteries stiffen? - CORRECT ANSWER -
refers to the elastic modulus of the wall material.
arteries stiffen towards the periphery and as you age
Describe pressure changes which occur throughout the circulation (4) - CORRECT
ANSWER - 1. Pressure begins high in the arteries; little resistance
2. Decreases slightly between aorta and arteries
3. Pressure decreases across the arterioles and capillaries; but resistance increases significantly
4. Pressure continues to drop in the veins; resistance decreases dramatically as well
Pulsatile changes in minute arteries, arterioles, and capillaries are reduced by
________________ and enhanced by ______________ - CORRECT ANSWER -
vasoconstriction
vasodilation
Pulsatile changes in small and medium arteries are reduced by _________________ and
increased by ______________ - CORRECT ANSWER - vasodilation
vasoconstriction
How does temporary cessation of forward flow or flow reversal occur? - CORRECT
ANSWER - A negative gradient is created after a wave has passed through one vessel but
is still traveling through a more distal one during the diastolic period of the cardiac cycle.
Flow reversal is generally only seen in which arteries? - CORRECT ANSWER - high
resistance (lower extremity) arteries
List the factors determining severity of a stenosis (7) - CORRECT ANSWER - 1. length
and diameter of the narrowed segment
2. roughness of the endothelial surface
3. degree of narrowing (abrupt or gradual)
4. ratio of cross-sectional area of narrowed segment to normal segment
, 5. rate of flow
6. arteriovenous pressure gradient
7. peripheral resistance beyond stenosis
Why is there more energy loss from tandem lesions than solitary stenosis? - CORRECT
ANSWER - there is a large loss of energy from disturbed flow patterns (jet effects,
turbulence, eddys)
more entrances and exits to lose energy at
Describe changes that may be seen in the pressure waveform distal to a stenosis (5) - CORRECT
ANSWER - 1. decrease in systolic pressure
2. decrease in amplitude of pressure wave distal to stenosis
3. dampening of pressure waveform
4. increased time to peak
5. greater width of pressure wave
What happens to the pressure waveform distal to a stenosis when blood flow is enhanced through
exercise or hyperaemia testing? - CORRECT ANSWER - The detectable decrease is
accentuated:
Enhanced blood flow through the stenosis will result in an increased loss of energy from friction
and velocity.
True or False?
At rest, it is possible to have normal blood flow in the presence of a severe stenosis or complete
obstruction - CORRECT ANSWER - True, the overcompensation by the cardiovascular
system is not sufficient to pass the occlusion and the flow can appear normal
You will only really see changes in blood flow at rest when? - CORRECT ANSWER - If
the occlusion is acute or there are more than one in series
