LV size
LVIDd Males
LVIDd Females
Pericardial Tamponade
Pericardial Tamponade
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1. How to obtain: Parasternal Long Axis Ultrasound View
2. How to obtain: Parasternal Short Axis Ultrasound View
3. How to obtain: Apical 4 (Four) Chamber Ultrasound View
4. How to obtain: Subcostal Cardiac Ultrasound View
5. How to obtain: Inferior Vena Cava Ultrasound View
Videos by Ultrasound Critical Care
FUSIC Heart Anatomy
Each view on echocardiography shows different cross sections of the heart. Here are labelled images seen within each window.
LA = Left Atrium
LV = Left Ventricle
RA = Right Atrium
RV = Right Ventricle
RVOT = Right Ventricular Outflow Tract
Ao = Aorta
AV = Aortic Valve
MV = Mitral Valve
TV = Tricuspid Valve
IVS = Intra-ventricular septum
IAS = Intra-atrial septum
IVC = Inferior vena cava
HV = Hepatic vein
Below are labelled images of the different FUSIC Heart views. Slide the middle cursor across to view either the labelled or unlabelled image ↔︎
A4Ch ↔︎
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Labelled
PLAX ↔︎
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PSAX ↔︎
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SC ↔︎
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SC IVC ↔︎
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FUSIC Heart Assessment
- FUSIC heart clinical questions:
Left ventricular assessment
The left ventricle can be assessed from the:
- PLAX – LV size and function, RWMA
- PSAX – LV function, RWMA
- A4Ch – LV function, RWMA
- Subcostal views – global impression
Each view will give an impression of the size of the LV and the function of the LV.
The questions that FUSIC Heart tries to answer regarding the left ventricular are:
1. Is the LV dilated?
The most common way to measure LV dilatation is in the PLAX view where the LV internal dimension in diastole (LVIDd) is taken.
End diastole can be determined in a few ways, these are:
1. The frame where the LV is at its largest
2. The frame after MV closure
3. The start of the QRS complex
When determine LVIDd in the PLAX view it is important to get good image optimization as any foreshortening of the LV could lead to inaccuracies in the measurements.
Normal LV: This is a PLAX view of the LVIDd (measuring at 4.92cm)
The measurement is taken using calipers to measure from the endocardial border of the septal wall of the LV to the endocardial border of the posterior free wall of the LV. This is taken at the level of the tips of the MV in systole (when they are open).
For the purpose of FUSIC heart the LV is determined to be dilated if the LVIDd >6cm
BSE reference for LVIDd
Normal
4.2-5.9 cm
3.9-5.3cm
Mild
6.0-6.3cm
5.4-5.7cm
Moderate
6.4-6.8cm
5.8-6.1cm
Severe
>6.8 cm
>6.1cm
It is worth noting the BSE reference for measuring LVIDd is different in both men and women. For example a LVIDd of 6.2cm would indicate mild dilatation of the LV in males but a severe dilatation of the LV in females.
Dilated LV: This is a PLAX view of the LVIDd (measuring at 6.22cm)
2. Is the LV significantly impaired?
When assessing the function of the LV it is important to assess how the LV is contracting, but is also important to assess for any regional wall motion abnormalities (RWMAs), and any reduction in wall thickening and motion. This assessment is done by ‘eyeballing’ the LV to get a global picture of how well it is contracting and performing a mitral annular plane systolic excursion (MAPSE) as a quantitative analysis.
Formal assessment of ejection fraction is an advanced echo technique and beyond the scope of FUSIC heart. There are a couple simpler methods that are worth knowing about and the MAPSE is part of the FUSIC heart curriculum. These are:
- Mitral annular plane systolic excursion (MAPSE)
- Fractional shortening
MAPSE
This is taken in the A4Ch view. As the LV contracts in systole in shortens longitudinally, radially and circumferentially. The distance that the MV lateral annulus travels in systole towards the LV apex is measured and this is known as the MAPSE.
To get the MAPSE value the A4Ch view is obtained and the M-mode line is placed over the lateral annulus of the MV. When in the correct position record M-mode by pressing the button again and freeze the screen once a few cardiac cycles have been recorded by M-mode. Place the calipers on the M-mode image and measure the lowest and highest points of the line of the MV.
MAPSE >12mm predicts normal LV function
MAPSE < 6mm predicts severe LV systolic dysfunction
MAPSE is good for distinguishing between normal and significant impairment of the LV, but is harder to interpret when the value lies between 6-12mm.
MAPSE measurement taken in M-mode with the cursor over the lateral mitral valve annulus.
Measurements taken from lowest to highest point of the line on M-mode representing the mitral annulus.
Fractional shortening
Fractional shortening can be useful because it is not too dissimilar to measuring the LVIDd. Again it is taken in the PLAX and LVIDd is measured, but at the same time LV internal diameter in systole is measured along the same plane as the LVIDd.
Systole can be determined by a few different ways:
- The frame where the LV is at its smallest
- The frame after AV closure
- The end of the T wave
This is a PLAX view of the LVIDs (measuring at 2.60cm)
Fractional shortening is then calculated using these 2 values:
FS = [(LVIDd – LVIDs)/LVIDd] x 100
This is a normal value for fractional shortening
BSE reference for fractional shortening
LV function
Fractional shortening
Normal
25-43%
Mildly impaired
20-24%
Moderately impaired
15-19%
Severely impaired
<15%
Fractional shortening can be prone to inaccuracies in RWMAs and if any foreshortening of the LV has taken place when obtaining the image. It does not take the whole of the LV into account and so can be prone to error.
RWMAs
In health the LV contracts and the walls thicken and they move equally towards the centre of the LV cavity. Whilst looking at the LV from the PLAX, PSAX and A4Ch it is important to assess how the LV is contracting in all the different areas of its walls.
RWMAs can be due to ischaemia such as in an acute coronary syndrome and in this case the RWMA will be in the area supplied by the affected blood vessel. The RWMA will look like reduced excursion and thickening in this case. For FUSIC heart one of the ways to assess for RWMAs is to look in the PSAX at the papillary muscle level. The LV should be circular and all areas of the LV should be contracting and thickening equally towards the centre.
The main blood supply from the heart is from the left and right coronary arteries. The left coronary artery divides from the left main stem (LMS) into the left anterior descending artery and the left circumflex artery (LCx). The LAD provides blood supply to the left anterior side of the heart and the LCx provides blood to the left lateral and posterior area of the heart. The right coronary artery (RCA) supplies blood to the right side of the heart – including the right atrium, ventricle, the sino-atrial (SA) node and atrioventricular (AV) node.
PSAX view showing antero-septal RWMA - note the reduced contractility in the upper left corner of the LV on this clip
Blood supply to the heart ↔︎
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PLAX view showing the areas of coronary blood supply to the LV
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PSAX view showing the areas of coronary blood supply to the LV
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A4Ch view showing the areas of coronary blood supply to the LV - the lateral free wall of the LV can sometimes be supplied by the LCx.
Summary
Using the knowledge of the assessments above and gaining experience in scanning the LV, over time, you will get better at using an ‘eyeball’ assessment of the LV and answer the questions:
- Is the LV dilated?
- Is the LV significantly impaired?
Right ventricular assessment
The RV can be assessed from the:
- PLAX – RVOT
- PSAX – RV size and septal shape
- A4Ch – RV size & function (TAPSE)
- Subcostal – global impression
If the patient has a dilated LV then this rule can lead to underestimating RV size, and if the image is foreshortened then this can lead to overestimating the RV size.
The main view for assessing the RV size and function is the A4Ch view but the other views can be helpful as well.
3. Is the RV dilated?
The main way to assess for RV dilatation is in the A4Ch view. This is done using an ‘eyeball’ assessment where the LV and RV are seen next to each other. The RV is determined to be normal size when the RV basal width is no more than 2/3 that of the LV.
RV is mildly dilated when it is >2/3 the basal width of the LV
RV is moderately dilated when it is equal to the size of the LV
RV is severely dilated when it is larger than the LV
The PSAX is not usually used to assess RV size but can give an indication of whether RV dilatation is present – see images below.
No RV dilatation - A4Ch view showing the RV roughly 2/3 the size of the LV and the LV is the apex forming ventricle
RV severely dilatation - A4Ch view showing RV basal diameter > LV basal diameter
PSAX view of a normal RV
PSAX view of dilated RV
If the patient has a dilated LV then this rule can lead to underestimating RV size, and if the image is foreshortened then this can lead to overestimating the RV size.
4. Is the RV severely impaired?
RV systole is predominantly in the longitudinal plane with some inward motion of the RV free wall. This makes the tricuspid annular plane systolic excursion (TAPSE) reflects longitudinal function and equates well with RV ejection fraction – making it ideal for measuring systolic function of the RV. The technique is similar to the MAPSE but performed on the lateral annulus of the tricuspid valve.
To measure the TAPSE get an optimal view in the A4Ch and place the M-mode line through the lateral annulus of the tricuspid valve. Press M-mode again and freeze the image after a few cardiac cycles. Measure using callipers the distance from the highest to the lowest point of lateral annulus of the tricuspid valve.
BSE reference values for TAPSE:
- TAPSE ≥17 is normal
- TAPSE <10mm is severely impaired.
TAPSE assessment using M-mode with a measurement of 2.05cm from the lowest to the highest point of the lateral annulus of the tricuspid valve. This is a normal TAPSE.
TAPSE assessment using M-mode with a measurement of 0.95cm from the lowest to the highest point of the lateral annulus of the tricuspid valve. This indicates the RV is severely impaired.
5. Is there evidence of low preload? (vasodilation/hypovolaemia)
The methods used to assess for low preload within FUSIC heart are inferior vena cava (IVC) assessment, combined with LV/RV assessment.
In a low preload state, which can be either due to vasodilation (for example in sepsis), or hypovolaemia (for example in dehydration/blood loss), the LV and RV will appear on echo to be hyperdynamic to try and increase the cardiac output through increasing the heart rate or contractility. This can be assessed in all views but may be well visualized in the A4Ch view.
In severe hypovolaemia there may be evidence of papillary muscle apposition in systole in the PSAX view. This gives the impression that most of the LV is emptying during systole and is evidence that there is low preload and the LV is underfilled.
The IVC assessment is also used to assess preload, however, it will differ depending on whether the patient is spontaneously breathing or is mechanically ventilated – which is not ideal for the ITU population for which FUSIC heart is used.
IVC
The IVC is assessed using the subcostal view with the probe rotate through 90 degrees anticlockwise from the original view of the heart. This brings into view the IVC in its long axis passing through the diaphragm and draining into the right atrium. Using M-mode place the line through the IVC perpendicular to its walls 1-2cm before its junction with the RA. Measuring on the M-mode image the maximum and minimum distance using calipers, as the IVC diameter changes with respiration.
The IVC diameter changes with respiration due to a negative intrathoracic pressure during inspiration and a positive intrathoracic pressure during expiration. During inspiration the negative intrathoracic pressure draws blood from the IVC into RA and the diameter reduces. During expiration the opposite occurs. This is during spontaneous respiration.
Normal IVC diameter is 1.5-2.1cm – outside of these limits suggest hypovolaemia or well-filled fluid status.
Limitations of IVC measurement
The IVC size and reactivity can be affected by multiple factors, including:
- Raised intra-abdominal pressure
- Tricuspid regurgitation
- RV failure
Spontaneous breathing and IVC assessment
An IVC diameter <2.1cm with collapsibility >50% with a sniff suggests right atrial pressure (RAP) 0-5mmHg
An IVC diameter ≥ 2.1cm with collapsibility <50% with a sniff suggests RAP of 15mmHg
Assume a RAP of 8mmHg for any other value that dies not meet the criteria above
SC IVC view in a spontaneously breathing patient with a sniff
SC IVC M-mode assessment of collapsibility with a sniff. Callipers can be used to measure between the largest and smallest diameter of the IVC.
Mechanically ventilated and IVC assessment
During mechanical ventilation there is positive intrathoracic pressure during inspiration and reduced intrathoracic pressure relatively in expiration. So the phasic collapse of the IVC is reversed.
The assumption is made that a dilated IVC with low respiratory variability reflects a high RAP (high preload).
A small IVC with high respiratory variability reflects a low RAP (reduced preload).
IVC measurement in M-mode showing a dilated IVC (2.57cm) with very little respiratory variation indicating a raised RAP - this could be due to RV failure or fluid overload
Putting LV and RV assessment together
So far we have seen how we can assess LV and RV size and function. It is important to be aware of the differences between the LV and RV and why they behave in the way they do with either pressure or volume overload.
Difference between LV and RV
The RV walls are thinner and the RV walls more compliant. This means the RV dilates acutely when exposed to pressure and volume overload. When dilatation is seen in the LV this is almost always due to chronic disease.
The LV perfusion is only in diastole due to the higher pressures in the myocardium during systole and compression of intramuscular vessels.
The RV is perfused in systole and diastole and predominantly supplied via the right coronary artery (RCA).
Difference between pressure and volume overload of the RV
In both severe pressure and volume overload RV dilatation is seen with a D-shaped septum on the PSAX view. In normal circumstances the LV is circular with the inter-ventricular septum bowed towards the RV. In conditions of pressure or volume overload the IVS can start to flatten and become D-shaped.
Depending on which phase of the cardiac cycle the IVS appears D-shaped will determine whether it is pressure or volume overload or a combination of the both.
Pressure overload – the IVS is D-shaped in systole
Volume overload – IVS is D-shaped in diastole, paradoxical septal motion may be present where hyperdynamic ventricles appear to move the septum anteriorly during systole.
Combination of both pressure and volume overload – IVS appears D-shaped throughout both systole and diastole.
In both pressure and volume overload the IVC will start to dilate >2cm and there will be minimal respiratory variability.
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PSAX view with a normal circular LV ↔︎
PSAX view of a D-shaped septum in both systole and diastole - indicating both pressure and volume overload
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PSAX view with a flattened inter-ventricular septum making the LV appear D-shaped ↔︎
6. Is there pericardial or pleural fluid?
Assessment for pericardial fluid should be made in all views of the heart. Fluid on echo appears anechoic (black) and for it to be pericardial fluid needs to be between the myocardium and the pericardium. It is normal to see very small amounts of pericardial fluid in some patients. In patients with high body fat content the epicardial fat pad can appear similar to pericardial fluid, however this has a much more granular appearance which can help distinguish it and it is usually small. The pericardial collection can either be concentric or localized and it is best seen in the PLAX and SC views.
To distinguish between pericardial and pleural fluid this is best done in the PLAX view. Pericardial fluid appears anterior to the descending thoracic aorta whereas pleural effusions are posterior to the descending thoracic aorta.
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PLAX view showing a small amount of pericardial fluid below the infero-lateral wall of the LV. ↔︎
Note: The fluid is anterior to the descending thoracic aorta meaning it is pericardial and not pleural fluid
This is best distinguished in the deep PLAX view.
PLAX view showing a small amount of pericardial fluid below the infero-lateral wall of the LV.
The pericardial effusion size can be measured at end diastole perpendicular to the pericardium and myocardium.
Pericardial effusion size
Small < 0.5cm Moderate 0.5-2cm Large >2cm
Maximal measurements around each regional wall should be made.
The appearance of the effusion can help distinguish its cause:
Simple effusion – uniform, anechoic
Exudative/fibrinous – stranding/loculation
Old blood – echogenic & grainy
Acute blood – similar to simple serous effusion
Purulent effusion – echogenic
Deep PLAX view demonstrating fluid posterior to the descending thoracic aorta meaning that it is pleural fluid.
Are there any signs of tamponade?
Early signs of pericardial tamponade are:
- IVC dilated, not collapsing
- RA collapse in systole
Late sign:
- RV early diastolic collapse → significant haemodynamic compromise
Very late sign:
- LV/LA collapse
SC view with evidence of pericardial fluid
Peri-arrest echo – where it fits in
Focused echo can be used during cardiac arrest and fits into the ALS algorithm at the pulse check. Usually the only place to assess the patient is via the subcostal view and limited to only 10 seconds.
Echo during cardiac arrest can help distinguish between true PEA (where coordinated electrical activity is seen on the monitor but there is no cardiac movement on echo and no palpable pulse) and pseudo PEA (where there is coordinated electrical activity on the monitor but there is cardiac activity on echo but with no palpable pulse).
Resus council recommendations for USS imaging during ALS:
- Only skilled operators should use intra-arrest point-of-care ultrasound (POCUS).
- POCUS must not cause additional or prolonged interruptions in chest compressions.
- POCUS may be useful to diagnose treatable causes of cardiac arrest such as cardiac tamponade and pneumothorax.
- Right ventricular dilation in isolation during cardiac arrest should not be used to diagnose massive pulmonary embolism.
- Do not use POCUS for assessing contractility of the myocardium as a sole indicator for terminating CPR.
Content created by Ben Stoney
Design by Max Broadbent
The ultrasound images and clips used on this website have be reproduced following the local clinical governance guidance.
