Question 9
How can ECHO be used to assess LV function?
LV function can be assessed in the following ways
- Fractional shortening
- “Eyeballing“ of LVF
- Ejection fraction (EF) – Simpson method
- Stroke volume
- Systolic index of contractility dP/dt
- Longitudinal contraction using tissue Doppler
- MAPSE
1. Fractional shortening:
- Measures the “squeeze “ of the LV . Using M mode measure the end diastolic diameter and the end systolic diameter of the left ventricle in the PLAX view or the PSAX view
- Can measure LVEDD and LVESD using M mode or calipers
Disadvantages of FS:
- M mode cursor has to be exactly perpendicular to the myocardium and at the tip of the mitral valves. Improved if using calipers
- It measures myocardial function in one plane only
Inaccurate if there is
- LBBB
- dyssynchrony
- abnormal septal motion
- regional wall abnormalities
- poor image quality
2. Ejection fraction:
2 ways of measuring the Ejection fraction
- Fractional Shortening using Teichholz method : Inaccurate and is no longer recommended for clinical use at it extrapolation of the EF from one plane of the Left ventricle only
- Simpson’s method
Involves tracing the endocardial border of the LV in the Apical 4 C and the Apical 2C view (Biplane method) - Currently the only method recommended for calculating LV volumes and EF using 2D ECHO.
Disadvantages of the Simpson’s method:
- Takes time to do,
- Need to get good windows with good endocardial wall definition to enable accurate tracing of the endocardial borders.
Inaccurate if there is
- dyssynchony as it is difficult to define end-systolic and end diastolic frames
- beat to beat variations such as in atrial fibrillation. It requires several measurements for averaging
- regional wall abnormalities of LV segments which is present in views other than the four- or two-chamber view (posterolateral and anterior septal segments) is not fully accounted
3. Eyeballing:
Look at
- Inward motion of the endocardium
- The thickening of the myocardium
- The longitudinal motion of the mitral annulus
- The geometry of the ventricle
Disadvantage is that it requires a certain amount of experience
4. Stroke volume :
Stroke volume = LVOT VTI (in cm) X the area of the LVOT.
Disadvantages :
- Requires good 3 or 5 chamber views
- Requires good technique which involves aligning the PW Doppler beam parallel to and through the centre of blood flow column and placing the sample volume just above the aortic valve in the LVOT.
Inaccurate
1. dynamic LVOT obstruction such as
- severe hypovolaemia
- asymmetric LV septal hypertrophy
- compensatory hyperdynamic basal segments in anterior myocardial infarction
2. Moderate to severe aortic regurgitation. The regurgitant diastolic volume into the LV is added onto the LVOT VTI in systole so check for AR with colour Doppler first before using this technique
5. Systolic index of contractility:
- Place a CW Doppler beam through the centre of a mitral regurgitant jet
- Measure the slope between 1 and 3 m/s
- Reflects the instantaneous pressure difference between the LV and the LA during LV systole.
- Reduced if the slope is less than 800mmHg/sec.
Disadvantages
- Requires a good MR signal
- MR jet also needs to be central and not eccentric.
- Cannot be used in acute MR because of high left atrial pressures in acute MR
- May not be accurate in hypertension or aortic stenosis as it is influenced by preload, afterload, heart rate and myocardial hypertrophy
6. Tissue Doppler:
- Place the sample volume at the level of the lateral mitral annulus.
- The peak systolic velocity is measured .
- A velocity of > 5.4 cm/sec correlates with an EF > 50% with 89% sensitivity and 85% specificity
Disadvantages
- Angle dependent
- Difficult to differentiate the velocity generated by actual myocardial contraction and that produced by translational motion by akinetic myocardial segments when they are pulled by the adjacent normally contracting myocardium
7. MAPSE Mitral annular plane systolic excusion:
- Measures the lateral mitral annular movement towards the apex using M mode.
- Easy to aquire.
- A normal MAPSE is > 8mm.
Disadvantages
- Lateral mitral annulus needs to move in the same plane as the M mode cursor.
- Only represents longitudinal contraction of the left ventricle
References
- Ann Card Anaesth. 2016 Oct; 19(Suppl 1): S26–S34 Left ventricular global systolic function assessment by echocardiography Suresh Chengode