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ECHO 325 > Doppler Review > Flashcards

Doppler Review Flashcards

1
Q

What is the formula for velocity of blood flow?

A

V = [f (Freq change) x C (spd of sound)] / 2 x fo (operating freq) x Cos theta

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2
Q

What is the main advantage of PW doppler?

A

Range specificity - Able to map velocities at any point in the heart

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3
Q

What are the two main things PW Doppler is limited by?

A
  1. Nyquist limit/PRF (aliasing)

2. Speed of sound in soft tissue

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4
Q

What is the Nyquist limit and when is it exceeded?

A

1/2 PRF

When the scale is exceeded (1/2 PRF) aliasing will occur

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5
Q

What is the main advantage of CW?

A

Can measure high velocities

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6
Q

What is the main disadvantage of CW doppler?

A

No range resolution (only the max velocity is measureable)

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7
Q

Why is TDI more intense?

A

Tissue is more dense

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8
Q

What relationship does the Bernoulli Equation outline?

A

The inverse relationship between velocity and pressure.

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9
Q

What is the simplified Bernoulli?

A

Change in P = 4V^2

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10
Q

How is the maximum pressure gradient calculated?

A

Using the Simplified Bernoulli formula but using the max velocity

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11
Q

How can pressure gradients be underestimated?

A

By not sampling completely parallel to flow

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12
Q

How would a 20 degree offset from flow direction affect the calculation of the blood flow velocity?

A

A 20 degree offset from flow direction = 6% underestimation of blood flow velocity

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13
Q

What must be done when calculating the velocity or pressure gradients in the presence of arrhythmias?

A

Measuring 3-5 beats and the averaging to find the answer.

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14
Q

3 factors that would lead to an underestimation of pressure gradients?

A
  1. Flow acceleration (prosthetic valves)
  2. Viscous forces (long stenosis over 10 mm, eccentric wall jets)
  3. Increased proximal velocities
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15
Q

When must the expanded Bernoulli equation be used?

A

When measuring velocities greater than or equal to 1.2 m/s

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16
Q

What is the “Peak to Peak” gradient?

A

When a catheter is used to derive the pressure gradient it measures the difference between the peak LV pressure and the peak aortic pressure

17
Q

In the presence of aortic stenosis, how is the doppler derived pressure gradient affected?

A

It will be higher than a normal AV and it will be higher than the catheter derived gradient as well.

18
Q

What is another name for stroke volume?

A

The volumetric flow rate

19
Q

What is the formula for SV?

A

SV = CSA x VTI

20
Q

What is the formula for CSA?

A

CSA = 0.785 x D^2

21
Q

How is VTI measured?

A

From a trace of the area under the spectral trace when doing CW or PW on the AV

22
Q

What is the formula for CO?

A

CO = (CSA x VTI x HR) / 1000

23
Q

How does the SV differ between the valves in a normal heart?

A

It doesnt, the SV should be the same in every valve.

24
Q

What is the formula for SV of a regurg valve?

A

SV regurg valve = SV competent valve + Regurgitant Volume

25
Q

What is necessary to calculate the Regurg Volume and what is the formula?

A

An estimation of the SV through the regurg valve

Regurg volume = SV regurg valve - SV competent valve

26
Q

What is the regurgitant fraction?

A

RF = Regurg volume / SV regurg valve

27
Q

What does Peak Velocity measure? (2)

A
  • Peak velocity

- Max Instantaneous Pressure Gradient

28
Q

If the area of a valve is reduced by half, how is the velocity affected?

A

It doubles

29
Q

What does Velocity Time Integral measure (VTI)? (4)

A
  • Peak velocity
  • Mean velocity
  • VTI (cm)
  • Max PG
  • Mean PG
30
Q

How does the VTI shape differ in the presence of stenosis?

A

Parabolic

31
Q

What does acceleration time measure?

A

The time is takes for any flow to reach its peak velocity

32
Q

What does deceleration time measure? (3)

A
  • Peak velocity
  • Deceleration time
  • Deceleration slope
33
Q

What is pressure half time?

A

The time it takes for the pressure to decay to half it’s original value

34
Q

What does the Pressure Half time measure?

A
  • Peak velocity
  • Slope
  • Pressure half time
35
Q

What is important to note about sweep speed?

A

It affects accuracy

36
Q

What does Delta P/Delta T measure?

A

The rise (or fall) of the pressure divided by the change in time when MR is present

37
Q

What must be increased in order to measure change in pressure / change in time?

A

Sweep speed to max setting

ECHO 325 (19 decks)

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