Doppler

Question 1

What can we assess with Doppler

Answer 1

• 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

Question 2

Appearance of envelope: brightest zone and spectral broadening

Answer 2

• Brightest zone of color spectrum = >RBCs
• Flow disturbance = marked spectral broadening of the time-velocity curve

Question 3

Define PG

Answer 3

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

Question 4

Limitations of modified bernoulli

Answer 4

 Slight overestimation of PG
 Blood volume, tunnel lesions (↑ friction), blood viscosity
 Intercept angle (inaccuracy)
 Valvular insufficiency + obstruction

Question 5

Why does Doppler derived PG overestimates PG

Answer 5

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

Question 6

What is assessed by PW TDI

Answer 6

provides myocardial mvt
o Color M-mode TDI: Myocardial velocities analyzed along a single line

Question 7

Applications of TDI

Answer 7

 Assessment of diastolic fct
 Myocardial synchrony
 Early detection of myocardial dysfct
 Qtfy myocardial functional reserve during stress echo for dx of CA dz

Question 8

Limitations of PW TDI

Answer 8

 Angle dependent
 May be affected by breed, age, HR
 Not discriminate active contraction of myocardium vs passive translational motion

Question 9

Quantitative clinical use of Doppler

Answer 9

PG
Peak velocities
Ventricular filling velocities
Regurgitant fraction
Pressure 1/2 time

Question 10

PG estimation specifics

Answer 10

• 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

Question 11

Abnormal high velocity flow develop in many cardiac conditions

Answer 11

AS, PS, HOCM, MR, TR, VSD, PDA
o Pressure gradient drives blood across the narrowed/restrictive orifice
* No angle correction: may overestimate pressure gradients

Question 12

Systolic LVP

Answer 12

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

Question 13

Systolic RVP

Answer 13

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

Question 14

Diastolic systemic P

Answer 14

AI peak velocity = PG btwn Ao and LV during diastole → close to 50 mmHg

Question 15

Diastolic pulmonic P

Answer 15

PI peak velocity → close to 10-15mmHg (2-2.5m/s)
o Early peak = mean PA pressure
o End diastolic peak = diastolic PA pressure

Question 16

Ao flow profile

Answer 16

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

Question 17

PA flow profile

Answer 17

• 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)

Question 18

Use of OT

Answer 18

estimate SV w CSA and VTI

Question 19

What is assessed by ventricular filling velocities

Answer 19

ventricular diastolic function

Question 20

Ventricular filling velocities are affected by

Answer 20

ventricular relaxation/distensibility, atrial pressure, AV pressure gradient, HR, loading conditions, ventilation, cardiac lesions

Question 21

Pattern of transmitral flow

Answer 21

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

Question 22

PV flow patterns

Answer 22

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

Question 23

IVRT

Answer 23

region of interest cross Ao and MV inlet to record interval from end of systolic flow to onset of diastolic flow

Question 24

Regurgitant fraction

Answer 24

o Flow to MV = flow to AoV
o MR: flow to MV > flow to Ao

Mitral RF = ((mitral SV – Ao SV))/(Mitral SV)

Question 25

Pressure 1/2 time AI

Answer 25

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

Question 26

Pressure 1/2 time MR

Answer 26

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

Question 27

Shunt quantification by Doppler echo

Answer 27

Doppler flow measurements at 2 cardiac sites → determine volume of blood flow
* Ratio Qp/Qs = pulmonary blood flow/systemic blood flow

Question 28

Continuity equation

Answer 28

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

Question 29

How to calculate volume of flow

Answer 29

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

Question 30

How to calculate area

Answer 30

CSA of vessel/orifice: CSA = r2
 Radius is the diameter of the vessel/area

Question 31

Is shunt fraction affected by regurgitation and Lv dysfct

Answer 31

Unaffected

Question 32

Qp equation

Answer 32

PA CSA + VTI PA

Question 33

Qs equation

Answer 33

LVOT CSA + VTI LVOT

Question 34

SV equation

Answer 34

CSA x VTI

Question 35

CO equation

Answer 35

SV x HR

Question 36

Limitations of shunt calculation

Answer 36

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