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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the main advantage of PW doppler?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the main advantage of CW?

A

Can measure high velocities

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the main disadvantage of CW doppler?

A

No range resolution (only the max velocity is measureable)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Why is TDI more intense?

A

Tissue is more dense

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What relationship does the Bernoulli Equation outline?

A

The inverse relationship between velocity and pressure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the simplified Bernoulli?

A

Change in P = 4V^2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How is the maximum pressure gradient calculated?

A

Using the Simplified Bernoulli formula but using the max velocity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How can pressure gradients be underestimated?

A

By not sampling completely parallel to flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

When must the expanded Bernoulli equation be used?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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
What is necessary to calculate the Regurg Volume and what is the formula?
An estimation of the SV through the regurg valve Regurg volume = SV regurg valve - SV competent valve
26
What is the regurgitant fraction?
RF = Regurg volume / SV regurg valve
27
What does Peak Velocity measure? (2)
- Peak velocity | - Max Instantaneous Pressure Gradient
28
If the area of a valve is reduced by half, how is the velocity affected?
It doubles
29
What does Velocity Time Integral measure (VTI)? (4)
- Peak velocity - Mean velocity - VTI (cm) - Max PG - Mean PG
30
How does the VTI shape differ in the presence of stenosis?
Parabolic
31
What does acceleration time measure?
The time is takes for any flow to reach its peak velocity
32
What does deceleration time measure? (3)
- Peak velocity - Deceleration time - Deceleration slope
33
What is pressure half time?
The time it takes for the pressure to decay to half it's original value
34
What does the Pressure Half time measure?
- Peak velocity - Slope - Pressure half time
35
What is important to note about sweep speed?
It affects accuracy
36
What does Delta P/Delta T measure?
The rise (or fall) of the pressure divided by the change in time when MR is present
37
What must be increased in order to measure change in pressure / change in time?
Sweep speed to max setting