Adult Echo - Module 3

Lectures 5-10

Start of Lecture 5

5

Explain the purpose of using M-mode.

• precise recording of the position and motion of cardiac muscle, valves, and surrounding tissue

• measurements can be compared against normal values

What is represented in the x and y axis of M-mode

x axis - time

y axis - depth

Name the primary limitation of M-mode.

If the M-mode line is not perpendicular with the anatomy, the measurement will be inaccurate

In an M-mode tracing of LV basal wall in PSLAX, list the measurements made and describe how to measure them

AoV

• curser where the AoV leaflets close in diastole

• aortic root diameter measured at end diastole from the tissue interface of the anterior wall of aortic root to posterior wall of aortic root

• LA measured at end systole from the trailing tissue interface to posterior tissue interface

MV

• cursor at the mitral valve leaflet tips

• E point septal separation - space between the anterior leaflet and anterior LA wall

LV basal wall

• cursor just past the mitral valve leaflets

• IVS measured at end diastole from the right to left surfaces of the IVS

• LVIDd measured at end diastole from the tissue edge of anteroseptal interface to tissue edge of inferolateral interface

• Inferolateral wall diameter measured in end diastole from the endocardial surface to epicardial surface of the posterior wall

• LVIDs measured at end systole from the tissue edge of anteroseptal interface to tissue edge of inferolateral interface

Normal value for LVIDd

W: 3.8 - 5.2cm

M: 4.2 - 5.8cm

Normal value for LVIDs

W: 2.2 - 3.5cm

M: 2.5 - 4.0cm

Normal value for IVS wall thickness

W: 0.6 - 0.9 cm

M: 0.6 - 1.0 cm

Normal value for posterior wall thickness

W: 0.6 - 0.9 cm

M: 0.6 - 1.0 cm

Normal range for aortic root

2.2 - 3.6 cm

Normal range for LA diameter

W: 2.7 - 3.8 cm

M: 3.0 - 4.0

What could cause a high EPSS (>5mm)?

• dilated LV

• mitral stenosis

• aortic regurgitation

Define TAPSE

Tricuspid annular plane systolic excursion

• from RV focused view

• TAPSE<16mm = RV dysfunction

How much does the IVC collapse during the sniff test with a healthy RA? What is expected with an unhealthy RA?

Healthy - collapse more than 50%

Unhealthy - collapse less than 50%

Why measure echocardiograms?

• echo exams can be standardized

  • study reproducibility

• distances can be measures accurately

• provides important diagnostic information

  • compare to normal values

• important for follow ups (progress)

List the phases of the cardiac cycle.

1. atrial systole

2. isovolumetric contraction time

3. rapid ejection 

4. reduced ejection

5. isovolumetric relaxation time

6. rapid filling

7. reduced filling

Name the two methods for calculating LV volumes from LV linear dimensions. Why are these not recommended for clinical use?

Teichholtz Method

Guinones Prolate Ellipsoid Method

Both rely on the assumption that the LV is a fixed geometric shape (prolate ellipse) - inaccurate assumption for many cardiac pathologies

Normal range for LV EF%

W: 54 - 74%

M: 52 - 72%

Normal range for FS

25 - 45%

A female patient has an EF of 45%. Is this normal? If no, what should the sonographer be looking for?

45% is lower than the normal range of 54-74%

This can be indictive of hypokinetic walls due to decreased contractility.

A female patient has an EF of 58%. Is this normal? If no, what should the sonographer be looking for?

58% falls within the normal range for a female.

When are 2D measurements used?

When M-mode is not optimal due to structures oblique to the cursor

What are some limitations of 2D measurements?

Lack of temporal resolution - may not get the optimal frame for measuring

Subject to more sonographer variability

Name the measurements made in PSLAX and when they are made.

End-diastole:

• Ao root

• IVS diameter

• LVIDd

• PW diameter

End-systole:

• LA diameter

• LVIDs

What are mechanical and electrical indicators of end systole?

Mechanical: frame after aortic closure, LV is smallest

Electrical: end of T-wave

What are the mechanical and electrical indicators of end diastole?

Mechanical: frame after MV closure

Electrical: peak R-wave

Where are measurements for the right heart imaged from?

Modified apical 4 chamber

SC 4 chamber

The LA used to be measured from the PSLAX anterior-posterior walls. Why is this no longer standard?

The relationship between the LA dimensions and the AP dimension is not maintained as the LA enlarges - inaccurate prediction of LA volume

Describe how the LA is measured.

In apical 4 chamber at end systole using an biplane area-length calculation

What is the difference between LAV and LAVI?

LAVI is the LAV indexed to body mass to make the measurement more diagnostic

Start of Lecture 6

6

The _______ method and ______ ______ ______ method are based on a single linear measurement of LV cavity made using 2D measurements in PSSLAX. These methods are not recommended for clinical use.

Teichholtz, Quinones prolate ellipsoid

Why are Teichholtz and Quinones methods not recommended for clinical practice?

• Assumes fixed ellipsoid shape, which does not apply to many cardiac pathologies

• Relationship between AP dimension and all other LA dimensions is not maintained as the atrium enlarges

FS =

(LVIDd-LVIDs) / LVIDd x 100%

EF =

(EDV-ESV) / EDV x 100%

When would a sonographer measure on a 2D image rather than in M-mode?

2D used when anatomy is not perpendicular to the scan line.

Name some advantages and limitations for 2D measurements.

Advantages

• able to be perpendicular to anatomy

• can be done in low PSLAX

• can be done in other standard windows

Limitations

• decreased temporal resolution

• can’t know the same wall position is measured in systole and diastole

• high intra-sonographer variability

• single dimension not representative for distorted ventricles

List some advantages and limitations for M-mode.

Advantages

• reproducible

• high temporal resolution

Limitations

• needs to be perpendicular to anatomy

• single dimension not representative for distorted ventricles

According to ASE, if the walls are not perpendicular in M-mode, you don’t need to acquire a trace if 2D measurements are used. (True/False)

False - ASE requires M-mode trace but can be without measurements.

What imaging plane and method is used for RV measurements?

Modified apical 4 chamber (RV focused apical 4 chamber)

2D measurements

What phase of the cardiac cycle is RV measurements made from? What 2D measurements are made?

End-diastole

4 measurements: one of length and 3 of width (basal, mid, and apical)

Normal range for RV wall thickness.

1-5mm

A sonographer collects measurements of the LA volume through a linear M-mode measurement and a biplane area-length calculation. Which value is smaller? Which value is more accurate?

Linear measurement is smaller because it underestimates LA volume

Biplane area-length calculation is more accurate

Normal range for LA volume indexed.

16-34mL/m²

LAVI = 

LA volume / BSA

Start of lecture 7.

7

If an echo is done accurately, it can…

• improve patient care and management

• reduce downstream repetitive testing (↑cost effectiveness)

• guide clinical outcome

  • diagnosis

  • prognosis

  • therapy

Achieving a reliable echo exam requires…

• understanding the standard imaging planes

• recognizing the optimal image

• utilize required modalities

• perform standard measurements with accuracy and precision

• recognize pathology and alter the scope of the exam to investigate

Reliability of a diagnostic test requires:

• accuracy

  • measurements are sensitive and specific

  • correct recognition of pathologies

• precision

  • reproducibility of study

• expertise

  • quality is dependent on sonographer and interpreting physician expertise

List some limitations to performing a reliable echo.

• small acoustic windows

• patient body habitus (poor images)

• pulmonary disease (artifact)

• patient cooperation (duration of study)

• presence of prosthetic valves (artifact)

• technical limitations and artifact

• sonographer expertise

An appropriate indication requires…

• initial diagnosis that will change clinical status

• results will change patient management

Start of lecture 8.

8

A Doppler shift is a measurement of…

The difference between the original frequency and the received frequency

The received frequency is less than the original frequency. What kind of Doppler shift is this? How would this appear on colour Doppler vs spectral Doppler.

Negative Doppler shift.

Appears as blue on colour Doppler.

Appears below the baseline in spectral Doppler.

Doppler in ultrasound is used to detect and quantify ______ and ______ in RBC.

direction, velocity

Doppler shift (Δf) =

(2 f_t V) cosθ / c

Doppler shift is ______ dependent.

angle

Why are most Doppler measurements made in the apical window instead of the PSLAX?

Doppler shift is only accurate when flow is parallel to the soundwave. Flow is most perpendicular in the apical window.

When Doppler is measured at a 20° angle from flow, there is __% and at 60°, error is __%.

7,50

List some advantages and limitations of pulsed wave Doppler.

Advantages:

• depth precision/range resolution

• distinguish laminar vs turbulent flow

Limitations:

• depth dependent → limited velocity range

What is the maximum velocity range of spectral PW Doppler? What is this limit called?

2 m/s → Nyquist limit

Define aliasing.

When the abnormal velocity exceeds the sampling rate, the PW system cannot record it properly and the display is of the other end of the velocity spectrum.

Velocity exceeds the Nyquist limit.

List some advantages and limitations of continuous wave Doppler.

Advantages:

• no Nyquist limit → information is displayed accurately

• not depth dependent

Limitation

• range ambiguity

• cannot differentiate turbulent and laminar flow

A spectral trace provides information about:

• direction of flow

• velocity of flow

• quality of flow

On a spectral trace, x-axis represents _____ and y-axis represents _____.

time, velocity

List some advantages and limitations of colour Doppler.

Advantages:

• displays quality of flow

  • larimar vs turbulent

  • antegrade vs retrograde

• hematologic information in relation to anatomy

• guides spectral Doppler sampling

Limitations:

• limited quantification

  • averaged velocity, not exact

  • limited maximum velocity (Nyquist limit)

Name the types of ultrasound Doppler.

• tissue Doppler imaging (TDI)

• spectral pulsed wave Doppler

• spectral continuous wave Doppler

• colour Doppler

TDI can assess…

• strain and strain rate

• myocardial mechanics and velocities

What modifications in signal processing does the machine need to do to accurately demonstrate TDI?

• increase amplification (receiving very low signals)

• filter blood flow signals (filter high velocities)

Why would a sonographer choose to listen to Doppler sounds?

More sensitive to audible changes than visible.

Compare 2D imaging and Doppler in terms of:

• what is measured

• goal of diagnosis

• type of information

• optimal alignment

• preferred operating frequency

2D imaging:

• measures tissue

• assesses anatomy

• structural information

• optimal perpendicular to structures

• prefers high frequency (↓SPL)

Doppler:

• measures blood (and tissue in TDI)

• assesses physiology

• functional information

• optimal parallel to blood flow

• prefers low frequency (↑SPL)

In a PW tracing, there is significant aliasing. Is there anything the sonographer can do to reduce aliasing?

Yes

• optimize baseline position

• increase velocity scale

• switch to CW

Provide some other names for sample volume box (SVB).

• sample volume (SV)

• range gate

• gate

Define vena contracta.

Narrowest central flow region a jet that occurs at the orifice of the valve. Characterized by high velocity, laminar flow.

What drives blood flow during the cardiac cycle?

Pressure gradients.

What is a pressure gradient?

Flow from areas of high pressure to areas of low pressure.

In an apical 5 chamber, CD shows blue at the AoV during systole. Does this represent antegrade or retrograde flow?

Antegrade.

In an apical 5 chamber, CD shows blue at the MV during systole. Does this represent antegrade or retrograde flow?

Retrograde.

List the windows and views the velocity and direction of LV inflow can be assessed. 

• apical 4 chamber

• apical 3 chamber

• apical 2 chamber

Define the E wave and what flows demonstrate an E wave.

Early diastolic filling (phase 6 of cardiac cycle)

• flow accelerates quickly to a maximum velocity

• flow decelerates as atria and ventricle pressures equalize

Seen with:

• LV inflow

• RV inflow

Define diastasis and what flows demonstrate diastasis.

Reduced filling (phase 7 of cardiac cycle)

• slow flow as atria and ventricle pressures equalize

Seen in:

• LV inflow

• RV inflow

Explain what happens to diastasis with increasing HR.

A fast HR has a very small diastasis because there is less time between rapid filling and atrial filling. This makes the E and A wave compressed closer because flow remains fast.

Define A wave and what flows demonstrate an A wave.

Atrial systole (phase 1 of cardiac cycle)

• atrial contraction reestablishes pressure gradient between atria and ventricle → ↑flow and velocity

Seen in:

• LV inflow

• RV inflow

Normal velocity range of E wave in LV inflow.

0.6-1.3 m/s

Normal velocity range of A wave in LV inflow.

0.2-0.7 m/s

Describe the E/A ratio. When would the E/A>1? When would E/A<1?

Difference between the pressure gradient in rapid filling and atrial systole.

>1 in young adults

<1 in older adults (>65 years old)

List the windows and views the velocity and direction of RV inflow can be assessed. 

• modified apical 4 chamber

• PSSAX at AoV

• PSLAX RV inflow

Normal velocity range for RV inflow.

0.3-0.7 m/s

How can LV inflow and RV inflow be differentiated on a PW trace?

V_MV > V_TV   

MV peak velocity closer to 1

↑spectral broadening in TV

↑variation in TV due to respiration (E and A wave height changes between cardiac cycles)

Normal velocity range for LVOT flow.

0.7-1.1 m/s

List the windows and views the velocity and direction of LVOT flow and AV flow can be assessed. 

• apical 5 chamber

• apical 3 chamber

Normal velocity range for AV flow.

1.0-1.7 m/s

Describe this trace in terms of:

• modality

• quality of flow

• peak velocity

• shape of the flow

• what is being measured

• PW Doppler

• laminar flow

• peak velocity at ~90cm/s

• monophasic laminar flow below the baseline that peaks at early systole

• LVOT is being measured

Describe what the red and blue arrows are indicating.

Red arrow → AoV opening (AoV opening click)

Blue arrow → AoV closing (AoV closing click)

Describe the SVB positions displayed.

1. LVOT - just proximal to AoV annulus 

2. Aortic flow - center of the aorta, close to cusp coaptation (vena contracta)

Normal velocity range for ascending aorta.

1.7 m/s

Normal velocity range for descending aorta.

1.7 m/s

What ultrasound modality would a cardiac sonographer use for quantifying flow through the aorta? Why? Name a limitation of using this modality.

CW

• no aliasing 

• highest velocity will be flow through the aorta and can be measured

• limitation - don’t know quality of flow

Describe this trace in terms of:

• modality

• quality of flow

• peak velocity

• shape of the flow

• what is being measured

• PW Doppler

• laminar flow away from the transducer

• peak velocity at ~1.2 m/s

• monophasic laminar flow below the baseline that peaks in early systole

• descending aorta or AV flow

Describe this trace in terms of:

• modality

• quality of flow

• peak velocity

• shape of the flow

• what is being measured

• CW Doppler

• CW does not assess quality of flow

• peak velocity of 5 m/s in diastole and 1 m/s in systole

  • high velocity indicates pathology

• no IVCT or IVRT - indicates regurgitation

• high velocities suggest AoV regurgitation