Ch 5 Parasternal CD Flashcards
What is the doppler effect?
A change in frequency caused by the motion of a sound source, receiver or reflector
Doppler echocardiography is based on the change in what?
In frequency of the backscattered signal from small moving structures (ex RBCs)
If the motion is moving towards, the received echo has a lower or higher frequency?
Higher
If the motion is moving away, the received echo has a lower or higher frequency?
Lower
What is a doppler shift?
The difference in frequency b/w the transmitted frequency (Ft) + the scattered signal received back at the transducer (Fs)
(DS = Fs - Ft)
What is the audible range of doppler shifts?
0-20 KHz
What is a positive doppler shift?
When the RBCs are moving TOWARDS the probe
What is a negative doppler shift?
When the RBCs are moving AWAY from the probe
Blood flow towards the probe is going to appear above or below the baseline?
Above (antegrade) - due to positive doppler shift in our color scale
Blood flow away from the probe is going to appear above or below the baseline?
Below (retrograde) - due to negative doppler shift in our color scale
Explain what each variable is in the doppler equation: V = c (Fs-Ft) / 2 Ft (cos)
V: velocity of blood flow
C: speed of sound in blood
Ft: transducer frequency
Fs: backscattered frequency
Cos: angle b/w ultrasound beam + direction of blood flow
When applying cardiac doppler, should the u/s beam be parallel or perpendicular to blood flow?
Parallel
Is cosine equal to 1 or 0?
Cos = 1
Will a doppler shift be recorded/detected if the u/s beam is perpendicular to blood flow?
Nope
Should we use angle correct for cardiac doppler applications? Why or why not?
No! B/c of the chance that the “correction” will be erroneous (wrong + inaccurate)
How can we avoid errors in calculating the velocity of blood flow?
By having the intercept angle of the u/s beam + the direction of blood flow parallel
What are the 2 intracardiac flow patterns we see in the heart?
Laminar + disturbed/turbulent flow
What is laminar flow?
Movement of fluid along well defined parallel stream lines with uniform flow velocities
In 3D, what does laminar flow consist of?
Concentric layers (lamina) or flow, each with a predictable + uniform direction and velocity
What is disturbed/turbulent flow?
Blood flow in multiple directions + velocities (is chaotic)
When would disturbed/turbulent flow occur?
Downstream from areas of narrowing
(ex: stenotic + regurgitant orifices or an intracardiac shunt)
Is a small amount of turbulent flow as the valves close normal in people?
Yes
What are flow velocity profiles?
Spatial distribution of velocities in a cross section: at a specific intracardiac location + at a specific time in the cardiac cycle
What is a flat flow velocity profile?
Parallel streamlines in a laminar flow pattern with the same velocity
(image shows all arrows in a straight line going in same direction)
List structures in the heart that would have flat flow velocity profiles?
-Flow across MV + TV
-Flow across prox AO + PA
What is a parabolic flow velocity profile?
Flow velocity is higher in the center + lower at the walls
(image shows arrows going in same direction, but not at same speed)
When would we see parabolic flow velocity profiles in the heart?
Once laminar flow is achieved in long, straight blood vessels under steady flow conditions
A blunted version of parabolic flow occurs due to what 2 things?
-Pulsing of vessels
-Shorter vessel length
What type of flow must be achieved before parabolic flow can?
Laminar flow - in long straight vessels under steady flow conditions
CD is a form of what?
PW doppler
CD uses multiple sample volumes along what?
Multiple scan lines
Are CD images angle dependent?
YES, must be parallel
CD is subject to aliasing once velocities pass what?
The nyquist limit (1/2 the PRF)
Is the nyquist limit higher or lower in CD?
Lower! B/c the mean doppler shifts/velocities are detected at each sample volume
(color nyquist limit is lower than in all other forms of doppler)
Is the color scale + the nyquist limit the same thing?
Yes
Does CD give us qualitative or quantitative info?
Qualitative
What is the min frame rate we want?
20
List 4 things that CD provides qualitative info on?
-A specific area of interrogation (color box)
-Direction of flow (BART + zero doppler shift appears black)
-Velocity of flow (not as specific as spectral doppler)
-Type of flow (laminar vs turbulent)
How to differentiate b/w laminar + turbulent flow with CD?
Laminar: smooth sold color pattern
Turbulent: aliasing with mosaic colors due to higher velocities
Is laminar or turbulent flow normal in the heart?
Laminar
How to differentiate b/w high + low flow velocities with CD?
High: brighter/vibrant hued colors which are farther away from the black zero doppler shift area on scale (baseline)
Low: deeper hued colors which are closer to the black zero doppler shift area on scale (baseline)
Do we use CD as a guide for spectral doppler interrogation?
Yes! For PW + CW
What is the general range our scale should be in?
50-90 cm/s (depends on structure of interest)
Why is it important to know the normal scale values for each valve?
Helps us optimize where to put our scale
What is regurgitation?
Backflow of blood through an incompetent valve
What is regurgitation in the semilunar valves called?
Insufficiency
What does valve regurgitation look like with CD?
Can be primarily one color or mosaic
What is a stenosis?
An area that is smaller than anatomically ideal
(m/c referred to with valves)
Stenosis can occur in specific anatomic locations due to what 2 factors?
-Hypertrophy
-Scarring
What does stenosis look like with CD?
Expect mosaic colors
What would intracardiac shunts appear with CD?
Can be primarily one color or mosaic
What would outflow tract obstructions appear with CD?
Mosaic
How would regurg, stenosis, shunts + outflow tract obstructions appear on CD?
Regurg + shunts: 1 color or mosaic
Stenosis + obstructions: mosaic
Explain how the flow travels in PLAX?
-Flows from LA through MV to LV
-Flows from LV through AoV to AO
In PLAX, where do we assess for potential anomalous (abnormal) flow?
Through the IVS (looking for possible ventricular septal defects)
What is the primary goal we want to establish in regards to flow in our views?
To establish normal laminar flow between structures
What color should flow be in PLAX as it moves from LV, LVOT into AoV during systole?
Red
(small amounts of blue due to change of direction in flow as valve closes)
What color would AoV regurg be in diastole in PLAX?
Blue
What would mosaic colors present at valves possibly indicate?
Stenosis or other valvular defects
(ensure scale is set appropriately)
What should we do to our scale if we are seeing a bunch of mosaic colors?
Increase scale to remove aliasing
Where should we put our CD box when assessing the AoV?
Extends from part of LV + goes just past AoV
(if regurg is seen, extend box over majority of LV to include whole jet)
What is the scale/nyquist limit range for semilunar valves?
60-90
(higher scale for these valves b/c they have higher velocity + pressure)
What color should flow be in PLAX as it moves from LA to LV in diastole?
Red
What color would regurg be from LV to LA in systole in PLAX?
Blue
Where should the CD box be placed when assessing the MV?
Should cover whole LA
What should the scale/nyquist limit range be for AV valves?
60-70
What is the primary goal when evaluating the IVS in PLAX?
-To ensure no shunt (abnormal communication) from LV to RV
-Can detect other flow accelerations + anomalies in LV such as LVOT obstructions
Where should the CD box be when assessing the IVS in PLAX?
Must cover entire length of IVS with overlap of RV + LV
(should be NO color passing b/w ventricles)
In RVIT, what color should flow be from the RA to RV in diastole?
Red
(can sometimes see red flow from IVC into RA)
In RVIT, what color would regurg be from RV to RA in systole?
Blue
Where should the CD box be when assessing the TV in RVIT?
Covers whole RA + slightly past TV
What would be the hemodynamic consequences of severe TV regurg in RVIT?
Would back up into venous circulation causing an increased fluid volume into IVC
In RVOT, what color should flow be as it moves from RV, RVOT into PV during systole?
Blue
In RVOT, what color would regurg be from PV in diastole?
Red
Where should the CD box be when assessing the PV in RVOT?
Extends above RVOT + along PA
Would stenosis of the PV cause increased afterload or preload?
Afterload of RV
(increases force + pressure the RV has to contract against + push blood into pulmonary circulation)
Does the PV or AoV have higher pressure?
AoV
What structures can we evaluate in PSAX - AoV?
-Flow over AoV
-Flow from RA, TV, RV
-Flow from RV, RVOT, PV, PA
-Potential anomalous/abnormal flow through IAS + IVS
In PSAX AoV, what color should flow be through the AoV in systole?
Red
(regurg from AoV to LV is blue)
Which view are we possibly able to view portions of the RCA + LCA?
PSAX AoV
(must lower scale b/c coronaries have lower velocity)
Where should we place our CD box when assessing the PSAX AoV?
Must fully cover the zoomed in AoV (assess IVS for VSDs)
(we are “enface” to the valve - meaning face to face with it)
What is the only exception where we would see flow exiting the AoV in PSAX AoV?
Within the coronaries (RCA, LCA), otherwise should NOT see flow exiting
In PSAX AoV - TV, what color should flow be when moving from RA to RV in diastole?
Red (regurg from RV to RA in systole is blue)
Mosaic antegrade flow through the TV indicates what?
Indicates TV stenosis
In PSAX AoV, where should our CD box be when assessing the TV?
Extends just past TV into RV + covers entire RA
In PSAX AoV - PV, what color should flow be when moving from RVOT, PV to RA in systole?
Blue (regurg from PA to RV in diastole is red)
In PSAX AoV - PV, anomalous/abnormal flow from below the PV from the right side of the PA could indicate what?
A patent ductus arteriosus
(remnant from fetal circulation)
In PSAX AoV, where should our CD box be when assessing the PV?
Extends just passed PV into the RVOT + includes majority of PA
What does color over the IAS tell us in PSAX AoV?
Tells us if there is communication b/w the LA + RA
(possible ASD)
What is a patent foramen ovale?
Failure of the fetal communication (foramen ovale) to close after birth
What is an atrial septal defect (ASD)?
Hole through IAS
What should the scale/nyquist limit range be set at to assess the IAS?
Decreased to 40-50
In PSAX MV, what color should flow be when moving from LA to LV in diastole?
Red (regurg from LV to LA in systole is blue)
Where should we place our CD box in PSAX MV?
Over MV and/or IVS (to look for abnormal communication b/w LV + RV)
What is the significance of clarifying “structure of interest”?
To clarify what the star of the show is + the reason why we are taking the image
Is PSAX PM CD clip always obtained?
Nope, only when wanting to evaluate for presence of a VSD
Where would we place our CD box in PSAX PM + apex?
Over entire IVS
(do this if we are expecting to see an IVS defect)
Is PSAX apex CD clip always obtained?
Nope, only when wanting to evaluate for presence of a VSD
What is the most important factor when optimizing for doppler imaging?
The alignment of the u/s beam!!
-Perpendicular to flow = no doppler shift
-Be as parallel as possible (tilting + rotating helps align the beam)
List 5 things we can adjust to optimize the controls for CD imaging?
-Color box size
-Velocity scale (nyquist limit)
-CD + 2D gains
-Wall filter
-Baseline
The CD box is adjustable in what 3 ways?
Position, length + width
The size of the CD box affects what?
Frame Rate: larger box reduces FR + makes image quality worse
Scale: longer + deeper boxes reduce PRF
Under what circumstances would we increase our scale?
-Reduce aliasing
-Smooth flow in high velocities of normal
Under what circumstances would we decrease our scale?
For visualization of slower velocity flow
What size CD box is best?
Shorter boxes with shallow depths
Is it possible to make things look worse/better than what they are accidentally when adjusting our scale + gains?
Yes! Ensure settings on machine are right
Does color have difficulty overriding grayscale at times?
Yes
What technique do we do to ensure we are at correct CD gains?
Increase the gain to where we see “speckling”, then decrease it to right below that
(must optimize + adjust CD gain in each view)
What does adjusting our wall filter do?
Enables removal of doppler shifts from display
What happens when we increase + decrease our wall filter?
Increase/high filter: excludes low velocity signals from valves or walls
(image shows correct vessel fill in)
Decrease/low filter: allows visualization of low velocity flow
(image shows color bleeding outside vessel)
Where is the baseline typically set?
In middle of color scale (black area) - but can be moved in 1 direction or another to remove aliasing
What is the baseline especially useful for?
Measurements for evaluating regurg
When would we shift the baseline?
When pathology is present
