Doppler Flashcards
What can we assess with Doppler
- Instantaneous direction of blood flow along key anatomic point
- Instantaneous velocity of blood w/I sample volume or along line of interrogation (CW)
- Absence/presence of disturbed flow
Appearance of envelope: brightest zone and spectral broadening
- Brightest zone of color spectrum = >RBCs
- Flow disturbance = marked spectral broadening of the time-velocity curve
Define PG
pressure in driving chamber > receiving chamber
o Pressure of receiving chamber calculated and added to gradient to estimated driving chamber P
o Conservation of energy → calculate pressure gradient from 2 areas of the heart
Constant volume of blood moved to specific area → ↑ pressure proximal to obstruction = α ↑ in blood flow velocity
Limitations of modified bernoulli
Slight overestimation of PG
Blood volume, tunnel lesions (↑ friction), blood viscosity
Intercept angle (inaccuracy)
Valvular insufficiency + obstruction
Why does Doppler derived PG overestimates PG
o Doppler derived PG: overestimation vs KT
Maximal instantaneous peak pressures pre and post obstruction → not occur at same time
Discrepancy invasive vs non invasive measurements: instantaneous gradients can be 30-40% ↑ than peak to peak
Severe stenosis = closer to peak to peak
What is assessed by PW TDI
provides myocardial mvt
o Color M-mode TDI: Myocardial velocities analyzed along a single line
Applications of TDI
Assessment of diastolic fct
Myocardial synchrony
Early detection of myocardial dysfct
Qtfy myocardial functional reserve during stress echo for dx of CA dz
Limitations of PW TDI
Angle dependent
May be affected by breed, age, HR
Not discriminate active contraction of myocardium vs passive translational motion
Quantitative clinical use of Doppler
PG
Peak velocities
Ventricular filling velocities
Regurgitant fraction
Pressure 1/2 time
PG estimation specifics
- Normal: peak diastolic and systolic pressure at either side of a valve are equal
o Do not occur at same time
o Peak to peak pressure gradient = 0
Instantaneous pressure gradient can be detected (2-10mmHg)
Typically small, drive blood through circulation - RBC velocity 0.25-1.7m/s
Abnormal high velocity flow develop in many cardiac conditions
AS, PS, HOCM, MR, TR, VSD, PDA
o Pressure gradient drives blood across the narrowed/restrictive orifice
* No angle correction: may overestimate pressure gradients
Systolic LVP
systemic pressures:
o Systolic LV pressure = peripheral systolic BP in absence of LVOTO
o Peak MR jet: driving pressure = LV systolic pressure = systolic BP → expect PG close to 100mmHg
Systolic RVP
pulmonary pressures
o Systolic RV pressure = pulmonary systolic pressure in absence of PS
o Peak TR jet = RV systolic pressure = systolic PAP → expect PG close to 20-25mmHg
Higher velocity suggestive of ↑RVP and PAPs
Diastolic systemic P
AI peak velocity = PG btwn Ao and LV during diastole → close to 50 mmHg
Diastolic pulmonic P
PI peak velocity → close to 10-15mmHg (2-2.5m/s)
o Early peak = mean PA pressure
o End diastolic peak = diastolic PA pressure
Ao flow profile
o Rapid acceleration, sharp peak
Peak depend on SV and CSA
Vary with ∑ activity, cardiac cycle length, sedation, obstructive lesions
o Deceleration: slower, 2x thickness of acceleration limb
o AI uncommon in healthy dogs
o STI of ventricular ejection: PEP, LVET → measured from Doppler flow
PA flow profile
- PA velocity: slower to accelerate, rounded peak
o Velocity time integral: vary beat to beat → respiration
Ventricular filling: ↑RV SV in inspiration
Translational movement of the heart
o PH: sharp, pointed peak, ↓AT, notch in deceleration
o PI common in normal dogs, low peak
With PH, higher velocities (higher pressures)
Use of OT
estimate SV w CSA and VTI
What is assessed by ventricular filling velocities
ventricular diastolic function
Ventricular filling velocities are affected by
ventricular relaxation/distensibility, atrial pressure, AV pressure gradient, HR, loading conditions, ventilation, cardiac lesions
Pattern of transmitral flow
Tips of opened MV
o M shaped wave form: early filling + atrial contraction
Early filling = E wave → rapid acceleration to peak, slower deceleration
Diastasis: minimal flow
Atrial contraction = A wave → follows P wave
o Stronger signal if: high CO state, L to R shunt, anemia, severe MR, tachycardia
o Areas under 2 triangles = V TI → estimate relative filling fractions
PV flow patterns
o Flow across PV driven by PG from PV → LA, influenced by diastolic and systolic LV fct
o Polyphasic
2 systolic forward flow waves (S) +/- Reversal wave
* Suction form MV annulus descent
* Retrograde RV SV
Early diastolic forward flow wave (D)
* Venoventricular PG
Late diastolic reversal wave (ar)
* Atrial contraction
* ↑ if resistance to ventricular filling, elevated ventricular pressures, ↑atrial pressures
IVRT
region of interest cross Ao and MV inlet to record interval from end of systolic flow to onset of diastolic flow
Regurgitant fraction
o Flow to MV = flow to AoV
o MR: flow to MV > flow to Ao
Mitral RF = ((mitral SV – Ao SV))/(Mitral SV)
Pressure 1/2 time AI
o Time for peak velocity to ↓ by ½
o AI: flow profile can indicate regurgitation severity
Rapid decline in in AI velocity (triangular shape profile vs plateau)
* Rapid decline in Ao pressure because of diastolic runoff in AI
* LV pressure also decline and PG ↓ = ↓ regurgitation
Diastolic ½ time: <300m/s suggest hemodynamically significant AI
Pressure 1/2 time MR
o M/TV stenosis
Severe stenosis → longer pressure ½ time
↓ slope → delayed early filling → persistent pressure differential → delayed MV/TV closure
Normal MV pressure ½ time: <29 +/- 8 ms in dogs, <30ms in cats
Shunt quantification by Doppler echo
Doppler flow measurements at 2 cardiac sites → determine volume of blood flow
* Ratio Qp/Qs = pulmonary blood flow/systemic blood flow
Continuity equation
flow proximal = flow distal
o Mass = density (D) x volume (V) x area (A)
Density is constant
Q1 = V1 x A1 = V2 x A2 = Q2
How to calculate volume of flow
by tracing flow profiles to determine the area under the curve (VTI)
Can be done at any of 4 valves
Can also be calculated: VTI = (Peak velocity x ET)/2
How to calculate area
CSA of vessel/orifice: CSA = r2
Radius is the diameter of the vessel/area
Is shunt fraction affected by regurgitation and Lv dysfct
Unaffected
Qp equation
PA CSA + VTI PA
Qs equation
LVOT CSA + VTI LVOT
SV equation
CSA x VTI
CO equation
SV x HR
Limitations of shunt calculation
o Measurements from R side: high variability
Most likely 2nd to variability in PA measurement (poor lateral wall resolution)
o MV stroke volume: high variability
Variability when measuring MV annulus size
