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Echo 2 > Module 1 : Doppler Review > Flashcards

Module 1 : Doppler Review Flashcards

1
Q

6 purposes of doppler in echo

A
  • detect areas of normal flow
  • detect areas of abnormal flow
  • differentiate between tissue and areas of blood flow
  • assess systolic function
  • assess diastolic function
  • provides functional info (pressure gradients through valves)
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2
Q

4 advantages to PW doppler

A
  • range specificity
  • adjustment of sample volume size and position
  • able to map any velocities at any point in the heart
  • 2D display
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3
Q

2 disadvantages to PW doppler

A
  • inability to measure due to aliasing

- limited by the speed of sound in tissue and PRF

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4
Q

main advantage to CW doppler

A
  • high velocity range (sample high velocities)
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5
Q

main disadvantage to CW doppler

A
  • no range resolution
    + only max velocity is measurable along a scan line
    + can’t be sure that a velocity is coming from a specific location
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6
Q

tissue doppler imaging TDI characteristics

A
  • movement of myocardial tissue not red blood cells

- TISSUE DOPPLER SIGNAL IS GREATER INTENSITY(brighter) = almost all echoes return

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7
Q

4 advantages to TDI

A
  • easily reproducible
  • provides other systolic and diastolic info in one waveform
  • can be performed on every patient
  • less volume dependant than MV inflow
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8
Q

5 disadvantages to TDI

A
  • TDI is angle dependant
  • ideally e primes measured at end expiration (larges e wave)
  • filter settings can vary between vendors
  • gain setting on Phillips to low
  • velocity will be lower than myocardium in rest of LV if they have (prosthetic valves, MAC, mitral annular ring)
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9
Q

baseline settings for spectral doppler

A
  • flow toward probe = baseline lowered to 1/4 from bottom
  • flow away probe = baseline raised to 1/4 from top
  • for pulmonary valve = baseline middle
  • wave form should take up 50% of available scale
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10
Q

speed of MR flow

A

5-7m/s

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11
Q

3 advantages to color doppler

A
  • sensitivity = can detect small amount of flow
  • region of interest = anatomic and hemodynamic info on one image
  • laminar vs turbulent = determine laminar flow from turbulent
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12
Q

2 disadvantages to color doppler

A
  • aliasing = blood flow exceeds color scale

- directional ambiguity = blood flow perpendicular confuses machine not sure where blood is flowing

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13
Q

Bernoulli equation relationships (velocity and pressure)

A
  • as velocity of a moving fluid increases the pressure within the fluid decreases
  • the drop in pressure creates a pressure difference between the region proximal to a narrowing and within the narrowing
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14
Q

simplified Bernoulli equation

A

P1 - P2 = 4V^2

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15
Q

maximum instantaneous gradient

A
  • calculated from a maximum velocity

- P max = 4V^2 max

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16
Q

mean pressure gradient

A
  • calculated by averaging the instantaneous gradients over the ejection period
17
Q

7 limitations of pressure gradient estimations

A
  • you must be parallel to blood flow
  • values are usually higher than invasively derived values
  • 20 degree offset from flow direction = 6% underestimation of velocity
  • must measure 3-5 beats when arrhythmias are present
  • significant flow acceleration
  • viscous forces
  • increased proximal velocities
18
Q

continuity principle

A
  • the volumetric flow rate (stroke volume) through a tube of a constant diameter is equal to the product of the criss sectional area(CSA) of the tube and mean velocity of fluid through the tube (VTI)
19
Q

stroke volume equation

A

SV = 0.785D^2 x VTI

20
Q

if there is no significant regurge or stenosis what will the volume of flow be through each valve

A
  • it will all be equal
21
Q

with a regurgitant valve what will eb the change in volume across the valves

A
  • the stroke volume through a regurgitant valve will be higher than a competent valve
22
Q

stroke volume through a regurgitant valve equation

A

SV rv = SV cv + RV

23
Q

regurgitant fraction equation

A

RF = RV / SV rv

24
Q

5 assumptions made by volumetric flow calculations

A
  • flow is occurring in a rigid circular tube
  • there is uniform velocity across the vessel
  • the rived CSA is circular
  • CSA remains constant throughout the period of flow
  • the PW sample volume position remains constant
25
Q

3 realities of volumetric flow calculation s

A
  • the heart and vessels are flexible and changing shape throughout the cycle
  • annular diameters may change throughout the cycle
  • MV and TV annuli are more elliptical than circular
26
Q

5 errors with SV calculations VTI method

A
  • non parallel to the flow leads to underestimation
  • failure to trace the modal (bright) velocity
  • incorrect placement of sample volume
  • filter settings
  • failure to average several beats
27
Q

3 errors with SV calculations diameter

A
  • measurement of the diameter during the wrong phase of the cardia cycle
  • inconsistant annulus measurement
  • difficulty in measuring in the RVOT
28
Q

what should the baseline be adjusted to

A
  • according to direction of flow of interest

* ** 3/4 the way from the top or the bottom**

29
Q

what should the velocity range (scale) be adjusted to

A
  • adjust the scale after the baseline is adjusted
  • useful part of the spectral should occupy 1/2 to 3/4 of the total scale
  • make signal as big as you can without aliasing
30
Q

what 5 things does the velocity time integral VTI measure

A
  • peak velocity (m/s)
  • mean velocity (m/s)
  • VTI (cm)
  • Max PG (mmHg)
  • Mean PG (mmHg)
31
Q

can the VTI be used for any valve

A
  • yes
32
Q

what is the acceleration time

A
  • time it takes for any flow to reach its peak velocity

- measured in milliseconds

33
Q

deceleration time measures what 2 things

A
  • peak velocity (m/s)

- deceleration time (ms)

34
Q

what 3 things does pressure half time measure

A
  • peak velocity (cm/s)
  • slope (cm/s^2)
  • pressure half time (ms)
35
Q

when is it important to optimize sweep speed

A
  • whenever measuring time
36
Q

if you have a higher sweep speed do you see more or less spectral trace

A
  • see less waveforms
37
Q

is a higher or lower sweep speed better for time measurements

A
  • a higher sweep speed
38
Q

what does the change in pressure / change in time represent

A
  • the rise or fall of pressure divided by the change in time
  • measures how quickly the LV can generate pressure
39
Q

when is Dp/Dt used the most

A
  • used to assess LV global systolic function

Echo 2 (18 decks)

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