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Cardiac 1 > Basics of Spectral Echo > Flashcards

Basics of Spectral Echo Flashcards

1
Q

Blood Flow Characteristics are based on:

A
  1. Type of vessel
  2. Size of vessel
  3. Resistance to flow
  4. Disease process which will make the vessel more narrow
  5. Phase of the cardiac cycle
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2
Q

What is rate of flow (flow rate) determined by?

A

Change in pressure between two areas and resistance to flow

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3
Q

What is the flow resistance influenced by?

A
  1. Length
  2. Viscosity
  3. Radius of a tube

(8 x L x viscosity/radius)

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4
Q

Poiseuilles law?

A

The relationship between pressure difference, flow rate, and resistance

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5
Q

Examples of types of plug flow?

A

Entrance to vessels or flow due to crossing valves

  1. RVOT and LVOT
  2. TV and MV
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6
Q

Examples of parabolic flow?

A

Occurs in long and straight vessels

  1. Peripheral vessels in cardiovascular system
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7
Q

In a curved vessel with skewed flow, where are velocities highest and lowest?

A

Highest on the outside of the curve

Lowest on the inside of the curve

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8
Q

In a U shaped vessel with skewed flow, where are the velocities the highest?

A

On the inside of the curve on the ASCENDING portion

On the outside of the curve on the DESCENDING portion

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9
Q

What type of flow occurs in a stenosis or bifurcation?

A

Disturbed flow

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10
Q

What type of flows are seen in a bifurcation of disturbed flow?

A
  1. Laminar flow on the straight portions of the vessel
  2. Slower, circular flow on the inside of the bifurcation branches
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11
Q

What is the term used for the slower, circular flow seen on the inner side of bifurcation branches?

A

Eddy flow

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12
Q

What are examples of turbulent flow?

A
  1. Stenosis
  2. Regurgitation
  3. Septal defects
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13
Q

What law explains “flow before a stenosis and after a stenosis must be equal” ?

A

Continuity principle

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14
Q

What formula explains change in pressure and velocity at a stenosis?

A

4(v)^2

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15
Q

As flow increases through a stenosis, what happens to the pressure?

A

There is an increase in pressure DROP

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16
Q

What is volumetric flow rate?

A

Velocity of flow x cross section area of a vessel

17
Q

When Cos = 1, what is the doppler shift?

A

It is at 90 degrees = perpendicular and NO FLOW

18
Q

What is on the ‘x’ and ‘y’ axis in spectral doppler?

A

x = time: adjusted via sweep speed

y = velocity

19
Q

Brightness and density of the spectral doppler signal equals?

A

Higher intensity and velocity and increased amplitude

20
Q

In what application can spectral broadening be seen?

A

Pulsed wave doppler

21
Q

What application is useful in detecting velocities at specific locations?

A

Pulsed wave doppler

22
Q

What does a higher PRF mean in terms of number of samples?

A

More samples being generated with a higher PRF

23
Q

How many samples does pulse wave need per cycle to prevent aliasing?

A

2

24
Q

What is nyquist limit?

A

Maximum doppler shift to avoid aliasing = 1/2 PRF

25
Q

Why is CW doppler a benefit?

A

It does not cause aliasing and can visualize high velocities

26
Q

How can you tell PW from CW?

A

PW has a spectral window and CW does not

27
Q

What is a disadvantage of CW?

A

Since it samples along the entire cursor line, it is tough to tell what depth the signal is coming from.

AMBIGUITY

28
Q

What probe has the best CW doppler signals?

A

Pedoff probe

29
Q

What are pedoff probes most often used for?

A

Stenosis - most commonly aortic

30
Q

As velocity increases, what happens to pressure?

A

Decreases

31
Q

What type of imaging records myocardial velocities?

A

TDI

32
Q

What is TDI used to determine?

A

LV diastolic dysfunction/function

RV systolic function

33
Q

If you image a higher velocity, what should you do to your baseline to accommodate the higher velocities?

A

Increase to accommodate visualizing higher velocities

34
Q

How much of the screen should a waveform take up?

A

2/3

35
Q

For faster heart rates, how do you adjust sweep speed?

A

Increased sweep speed to spread out waveform

36
Q

What would cause an increase in signal:noise ratio?

A

Increasing sample gate

37
Q

What is an optimal sample gate?

A

3mm

38
Q

What should you do to the wall filter in slower flow?

A

Decrease it to capture the slower flow

39
Q

What do wall filters eliminate?

A

High intensity, low-velocity signals (clutter)

Cardiac 1 (9 decks)

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