M1: Doppler Review Flashcards
what are the 2 main disadvantage of PW… what is its limitation and why
inability to measure high velocities
limited by speed of sound in soft tissue/PRF
cannot measure velocities above 2-2.5 m/s due to aliasing/nyquist limit
ideally, when should E prime waves be measured and why
at end expiration because they will be the largest
what doe green indicate on the doppler colour map
turbulence
what is a typical velocity for MR
5-7 m/s (use CW to measure)
list the 3 advantages of colour doppler
sensitivity (can detect small amount of abnormal blood flow)
region of interest
laminar vs turbulent flow
list the 2 disadvantages of colour doppler
aliasing
directional ambiguity: when blood flow is perpendicular to the beam, multiple colours will appear and direction of flow cant be determined.
Is TDI less or more preload dependant and MV inflow
Less
What pathologies cause velocities in the myocardium to be lower than the rest of the LV
Prosthetic valves
MAC
Mitral annular ring
Is TDI ANGLE dependant
Yes
3 pressure estimation methods
Bernoulli (velocity and pressure)
Mean pressure gradient
Max instantaneous pressure gradient
How is the max instantaneous pressure gradient calculated
Use the max velocity in the Bernoulli equation
How is the Mean pressure gradient calculated
By averaging the instantaneous gradients over the ejection period
Limitations of press gradient estimations
Under estimated by non parallel sampling (20 degree offset from flow direction = 6% under est)
Values not the same as invasively derived values
Measure 3-5 beats w/ arrthythmias and average velocities
Other factors that lead to under estimation of press gradients
Significant flow acceleration
Viscous forces
Increased prox velocities
How do our measurements compare to the cath lab
They will be slightly over estimated due to using Max pressure gradient….. cath uses peak to peak method (we only measure at one point in time, cath chooses highest peak at any point in time)
What is the VTI
Mean velocity
How does stoke volume change wit regurg
SV will be higher through the RV than competent valve
Formula for Regurg volume
RV = SC of RV - SV of CV
Formula for regurg fraction
RF = RV /SV of regurg valve
Assumptions of volumetric flow calculations
Flow occurs in a rigid circular tube
Uniform velocities
CSA is circular and constant throughout flow period
PW SV stays in same position
Shaped of MV and TV annulus
Elliptical
What does measuring peak velocity give you
Peak velocity and max/peak instantaneous PG
What happens to spend if valve area reduced by half
It doubles
What does VTI measurement give you
Peak velocity Mean velocity VTI MAX PG MEAN PG
What method can be used to measure MVA when valve is stenotic
VTI trace of MV Inflow
Which sweep speed is used for accurate time measurements
Fast
Dp/Dt can only be done when
When there’s MR
