Advanced Hemodynamics: Doppler Physics For Valvular Assessment Flashcards
What is the AVA formula?
((0.785 x D^2)(VTI))/VTI2
Or
(A1+V1)/V2
How do we calculate MVA?
Use a formula similar to AVA
What is a simple formula for AVA or MVA?
Stroke volume 1 = Stroke volume 2
Or
A1xV1 = A2xV2
What measurements do we need for formula for the MV?
- Measure LVOT
- LVOT PW trace (V1)
- Measure MV CW trace (V2),
What does PISA stand for?
Proximal isovelocity surface area
What is PISA radius?
When flow converges towards a small opening, it accelerates in a laminar manner forming a flow convergence zone
During PISA radius we have a series of concentric what?
Concentric hemispheric shells of the same velocity
In terms of PISA radias, as the flow gets closer to the hole what happens?
The diameter of each shell decreases as the velocity within each shell increases
In terms of PISA radius, a bigger shell equals what?
Bigger leak
When are we unable to use the LVOT as our control valve in the continuity equation?
- When we have aortic regurgitation
- When we have a long length of stenosis
How do we obtain PISA radius?
- Turn on colour
- Zoom MV
- Shift colour baseline between 20-40 cm/sec to produce aliasing
- Select PISA radius in MV mat package
- Measure radius from leaflet tips to top of aliased velocity
How do we find the PISA Radius: flow convergence zone?
- Use a A4C view with zoom and colour
- Baseline shifts down to 20-40 cm/s to enhance the hemispheric shells. (Baseline shift towards direction of flow)
- Measure vertical distance from leaflets to top of convergence zone (aliased interface)
Label the numbers
- Jet Height
- Flow convergence
- Vena Contracta
In terms of PISA, if we measure the peak regurgitation, we will be able to determine what?
The area of the regurgitation orifice
Because of PISA radius, we know that:
1. The aliasing velocity (the speed of the outside of the shell)
2. The radius of the shell
Which gives us what?
SV at the outside of the shell
To quantify MR with PISA, 4 variables are needed, what are they?
- PISA radius with colour doppler
- The aliasing velocity
- The peak velocity of the MR jet
- The velocity time integral VTI of the MR jet
Under pressure, due to the Bernoulli principle. Velocities are directly related to what?
The PG across the valve and so, we can use these PGs to estimate the pressures of the adjacent chamber
What is Bernoullis principle?
change in pressure = 4V^2
When using the Bernoulli principle, A VTI trace not only gives us the max pressure gradient, but what?
The mean PG
Under normal pressures which valve will have the highest velocity regurgitation jet?
The one with the most difference change in pressure.
This would be the one between the LA and the LV
What changes might increase the velocity of a regurgitation jet?
An increase in pressure on one side of the valve.
In terms of the Bernoulli’s principle, the mean PG tells us more of the story of what?
What is going on throughout the entire flow period
In terms of Bernoulli’s principle each point on the trace has what?
4(V^2) applied to it, resulting in an average pressure gradient over the diastolic cycle = mean PG
Why do we use MV inflow mean pressure gradient?
This is done because the waveform is not parabolic with a single peak like the AV and PV
In terms of the MV inflow mean gradient, the PG varies how ?
Throughout the diastolic cycle, this results in the diastole is longer than the systole
When assessing he AV we use what instead of peak velocity?
VTI
What do we use to trace the doppler envelope to obtain mean gradient?
CW doppler
How do we measure Mean TV pressure gradient?
Measured from the most parallel to TV flow
Measuring the TV VTI works the same way as the MV with one caveat, what is it?
Average VTI over several beats to account for changes in Venous return with respiration
Pressure half time is a measurement of what?
Of the time it takes for the early diastolic pressure gradient to half of its original value
In terms of MV/TV stenosis. A normal MV PG does what?
Decreases quickly
In terms of a MV/TV stenosis LA pressure is ______ LV pressure for only a short time during diastole, with the pressure quickly doing what?
- Greater
- Dropping down to less than LV again
In terms of Pressure half time what is the general rule for MV inflow?
Normal MV inflow = quick P(1/2)t
When the pressure in the LA is high due to MS, what happens to the LA pressure period? What does this mean in terms of pressure half time?
The LA pressure stays higher, longer. Therefore
Increased MS = increased P(1/2)t
Normal TV/MV wave = Short P(1/2)T
MVA can be derived by dividing what?
Divine 220 (a constant) by P(1/2)T
How do we calculate the TV pressure half time?
Same principle as MS
What is the limitation of PHT for TV?
Tachycardia
In terms of TV PHT, With TS, the PHT greatly does what?
Increase
In terms of PHT we can use the same concept of what? We use this to do what?
- How quickly pressure fall to assess AR/PR
- Compare the LV pressure to the Ao pressure during diastole
In terms of PHT, as AR severity increases what happens?
In terms of PHT for PR we use the same concept as what?
AR
What is the PR A-dip
- You may see the A dip in the PI waveform with normal PA pressure
- This happens just after the P wave
How can we summarize PHT in terms what is good and what is bad?
What is the formula for RVSP?
(4(TRvel)^2) +RAP
