Abstract
A systematic approach to transoesophageal echocardiography (TOE) is essential to ensure that no pathology is missed during a study. In addition, a standardised approach facilitates the education and training of operators and is helpful when reviewing studies performed in other departments or by different operators. This document produced by the British Society of Echocardiography aims to provide a framework for a standard TOE study. In addition to a minimum dataset, the layout proposes a recommended sequence in which to perform a comprehensive study. It is recommended that this standardised approach is followed when performing TOE in all clinical settings, including intraoperative TOE to ensure important pathology is not missed. Consequently, this document has been prepared with the direct involvement of the Association of Cardiothoracic Anaesthetists (ACTA).
1. Introduction
This document aims to provide a framework for performing an adult transoesophageal echocardiography (TOE) in a variety of clinical settings such as cardiology outpatients, cardiac theatre, and intensive care. The layout is not only a minimum dataset but also proposes a recommended sequence in which to perform a comprehensive study. This is supported by text that gives a brief description of important issues at each view (Tables 1 and 2, Fig. 1, Tables 3, 4, 5, 6, 7, 8, 9 and 10).
Table 1Assessment of the left ventricle.
View (modality) Measurement Explanatory note Image Mid oesophageal
Four-chamber, 0–20° (2D)Assessment of LV function: inferoseptum and anterolateral walls
May require extension of probe to bring apex in to view
Focus can be moved towards the apex to improve quality of image
Careful assessment for apical thrombus/massesMid oesophageal
Two-chamber, 80–100° (2D)LVDd/s Assessment of LV function: inferior and anterior walls
Measurements can be made with 2D calipers for LV dimensions at the junction of the basal and middle thirds of the LV (8)Mid oesophageal long axis, 120–150° (2D) Assessment of LV function: inferolateral and anteroseptal walls Table 2Assessment of the mitral valve.
View (modality) Measurement Explanatory note Image Mid oesophageal
Four-chamber, 0–20° (2D)Assessment of MV: several sections of the MV can be imaged in this view (see Fig. 1 for a full explanation)
Particular attention to the mitral annulus, leaflet morphology, leaflet motion, and the sub-valvular apparatusMid oesophageal
Four-chamber, 0–20° (2D)Assessment of MV: A1/P1
Flexion or withdrawal of the probe slightly will bring A1/P1 into view
The anterolateral commissure can be assessedMid oesophageal
Bi-commissural view, 60–70° (2D)Commissure to commissure annular dimension (end diastole and end systole) Assessment of MV: P3/A2/P1
The imaging plane now brings both commissures into view
This is an appropriate anatomical plane to measure the annular dimension (see Fig. 1)
From left to right, the scallops seen in this view are P3/A2/P1 as shown belowMid oesophageal
Two-chamber, 90° (2D)Assessment of MV: P3/A1 Mid oesophageal
Posteromedial commisure, 90° (2D)Assessment of MV: P3/A3
The posteromedial commissure can be seen by turning the probe towards the aorta and then coming back to the MVMid oesophageal
Long axis, 120–150° (2D)Anterior to posterior annulus dimension (end diastole and end systole) Assessment of MV: P2/A2
This is the second anatomical plane which allows the mitral annulus to be measured (see Fig. 1)All of these views should be reassessed with colour flow Doppler over the mitral valve. PW and CW should be used in either the four-chamber or long-axis views
Figure 1 (A) This figure depicts the different sections of the MV that are visualised in the standard mid oesophageal imaging planes. The four-chamber view at 0° is an oblique cut through the MV and will visualise different parts of the valve according to the depth of probe insertion, the degree of flexion/extension and also the anatomical lie of the heart which may vary between patients. This means that A3/A2/A1 extending to P2/P1 may be in view at any one time. It is not usually possible to image A3/P3 at 0°. (B and C) These panels illustrate the correct anatomical planes for annular dimensions – the bi-commissural view (B, major axis) and the long axis view (C, minor axis) (5). These measurements in end diastole and end systole provide useful data for the cardiac surgeon in the setting of mitral repair. There is a paucity of data for normal ranges indexed for body surface area.
Citation: Echo Research and Practice 2, 4; 10.1530/ERP-15-0024
Table 3Assessment of the aortic valve.
View (modality) Measurement Explanatory note Image Mid oesophageal
Short axis, 40–60° (2D)Assessment of the AV. Flexion/extension or insertion and withdrawal of the probe will allow imaging above and below the valve making sure to image at the leaflet tips to assess opening
The coronary ostia can be seen above the valveMid oesophageal
Long axis, 120–150° (2D)LVOT/aortic annulus The NCC is seen in the near field with the RCC in the far field
Movement of the probe from left to right is essential in this view to image the extremities of the valveMid oesophageal
Long axis, 120–150° (2D)LVOT/aortic annulus The LVOT dimension is measured in mid-systole from the septal endocardium to the anterior mitral valve leaflet ∼0.5–1 cm from the valve orifice (6)
The aortic ‘annulus’ is measured from the hinge points of the AV in mid-systoleThese views should be repeated with colour flow Doppler. Alignment is not possible for spectral Doppler. The four-chamber mid-oesophageal view can also be used with slight flexion or withdrawal of the probe in order to assess the ventricular aspect of the AV and also to image aortic regurgitation.
Table 4Assessment of the left atrium and left atrial appendage.
View (modality) Measurement Explanatory note Image Mid oesophageal
Four-chamber, 0–20° (2D)LA dimension in two axes The probe needs to be moved from left to right to image all parts of the LA completely
The LA area/volume can be difficult to obtain from TOE due to the proximity to the transducer.
Dimensions in two axes can be measured in this view (semi-quantitative)Mid oesophageal
Two-chamber, 90° (2D)As above, movement of the probe from left to right will maximise the chance of imaging all corners of the LA Mid oesophageal
Four-chamber, 0–20° (2D)The LAA can be imaged often helped by flexion or withdrawal of the probe slightly
Careful attention should be made to distinguish pectinate muscles from thrombus
The depth and focus can be adjusted to maximise the qualityMid oesophageal
LAA view, 60–130° (2D)It is essential to image the LAA in at least two planes. One or more lobes can be seen when the multiplane is turned beyond 90°
Movement of the probe to the left can keep the LAA in view
Look out for spontaneous echo contrastMid oesophageal
LAA view, 0–130° (CFM)Colour Doppler can help assess the extent of the LAA cavity Mid oesophageal
LAA view, 0–130° (PW)Emptying velocities PW Doppler can be placed within the mouth of the LAA (not more than 1 cm) in order to quantify emptying velocities Table 5Assessment of the inter-atrial septum.
View (modality) Measurement Explanatory note Image Mid oesophageal
IAS, 0–20° (2D)The interatrial septum is well seen on TOE due to its close proximity to the transducer
Lipomatous hypertrophy is frequently seen in this viewMid oesophageal
IAS, 40–80° (2D)The presence of a patent foramen ovale can be assessed in this view. Note the insertion of the Eustachian valve near the inferior vena cava in the right atrium Mid oesophageal
Bicaval, 80–120° (2D)It is essential to image the IAS in multiple views to exclude ASD/PFO. Sinus venosus defects can be easily missed by incomplete imaging of the IAS near the insertion of the IVC and SVC All of these views should be repeated with colour flow Doppler to look for ASD/PFO. Reducing the Nyquist limit may help to visualise low velocity flow across the septum. Always remember to reset the Nyquist limit for the rest of the study.
Table 6Assessment of the pulmonary veins.
View (modality) Measurement Explanatory note Image Mid oesophageal
Four-chamber, 0–20° (CFM)The upper pulmonary veins tend to insert more vertically into the LA. Flexion or withdrawal of the probe can bring into view
Note the close relationship of the LUPV to the LAAMid oesophageal
Four-chamber, 0–20° (CFM)The lower pulmonary veins tend to insert more horizontally into the LA.
Inserting the probe further and turning further to the left can help image the LLPVMid oesophageal
Four-chamber, 0–20° (CFM)After turning the probe to the right, flexion or withdrawal of the probe can help image the RUPV Mid oesophageal
Modified bicaval view, 90–110° (CFM)The RUPV can often be easier to image by starting with the bicaval view to visualise the SVC and then turning the probe further to the right whilst keeping the colour Doppler in position Mid oesophageal
Four-chamber, 0–20° (CFM)Inserting the probe further and turning the probe to the right can bring in the RLPV Mid oesophageal
Four-chamber, 0–20° (PW)The PW cursor is placed 1 cm into the mouth of any pulmonary vein but usually the LUPV is the best aligned
Two pulmonary veins should be analysed in each patientTable 7Assessment of right heart.
View (modality) Measurement Explanatory note Image Mid oesophageal
Four-chamber, 0–20° (2D)The right ventricle can be assessed in more detail for regional and global function
The septal leaflet is on the right with the anterior or posterior leaflet on the left depending on how far the probe is inserted (7)Mid oesophageal
Four-chamber, 0–20° (2D)RV size
Tricuspid annulusRV size can be assessed at the base and the mid point in end diastole (8)
The tricuspid annulus can be measured at end systole and end systole from hinge point to hinge pointaMid oesophageal
RV inflow/outflow, 60–80° (2D)Regional and global RV function can be further assessed
The posterior leaflet is on the left with the anterior leaflet to the right
The pulmonary valve can also be seen in this viewMid oesophageal modified RV inflow, 110–130° (2D) The tricuspid valve can also be imaged at this multiplane angle aided by turning the probe to the right Mid oesophageal modified RV inflow, 110–130° (CFM) This view often allows TR to be assessed using CW Doppler due to the vertical alignment Mid oesophageal modified RV inflow, 110–130° (CW) TR Vmax Doppler estimate of RVSP may be performed Mid oesophageal
RV outflow, 60–80° (2D)Pulmonary valve annulus The pulmonary valve is often better imaged by using the zoom Mid oesophageal
Main PA, 0° (2D)Main pulmonary artery The main pulmonary artery can be imaged by withdrawing the probe slightly at 0°. The pulmonary artery bifurcation is well seen with the right main pulmonary artery heading behind the ascending aorta Mid oesophageal
Main PA, 0° (CFM)Colour Doppler will demonstrate flow towards the transducer in systole All of these views should be repeated with colour flow Doppler to assess the tricuspid and pulmonary valves. PW/CW can be used to assess flow through the pulmonary valve in the mid oesophageal view at 0°.
Tricuspid annular dimensions in the four-chamber view provide useful data for the cardiac surgeon in the setting of tricuspid repair. There is a paucity of data regarding normal ranges indexed for body surface area.
Table 8Transgastric views – assessment of the left ventricle.
View (modality) Measurement Explanatory note Image Transgastric mid LV short axis, 0–20° (2D) IVSd
LVDd/sAfter insertion of the probe into the stomach, flexion will bring this image into view
Regional and global LV systolic function can be assessed
Chamber dimensions can be measured either with 2D calipers or M-mode placed vertically within the sector (8)Transgastric
Basal LV short axis, 0–20° (2D)Withdrawing the probe slightly will image the base of the LV with the MV enface
This is a good view for assessing the mitral commissures and imaging the site of MR with colour DopplerTransgastric
Two-chamber, 80–100° (2D)LVDd/s The inferior wall is seen within the near field with the anterior wall in the far field
LV dimensions may be obtained by 2D callipers or M-mode as for the short axis views (8)
This view is the best for assessing chordal pathology and lengthTransgastric long axis 90–120° (2D, CFM, PW, CW) Turning the probe slightly to the right may help image the AV Transgastric long axis, 90–120° (PW, CW) PW LVOT
CW AVmaxColour Doppler guides the alignment of PW in the LVOT and CW through the AV The mid oesophageal views do not allow spectral doppler analysis of the AV Deep transgastric, 0° (2D, CFM, PW, CW) PW LVOT
CW AVmaxThe probe is inserted further in to the stomach with flexion in order to obtain this image which is similar to a transthoracic apical five-chamber view
Colour Doppler can guide the use of PW in the LVOT and CW through the AVTable 9Transgastric assessment of the right heart.
View (modality) Measurement Explanatory note Image Transgastric
Short axis RV, 0–20° (2D)All three leaflets of the tricuspid valve can be seen in this view. RV regional and global function can be assessed Transgastric
RV inflow, 80–100° (2D)The tricuspid leaflets and the subvalvular apparatus are well seen. This is also an excellent view for assessment of pacing wires in the RV Table 10Assessment of the aorta.
View (modality) Measurement Explanatory note Image Mid oesophageal
Long axis aortic root, 120–150° (2D)Sinuses of Valsalva, sinotubular junction, and ascending aorta Internal dimensions can be measured in mid diastole (8)
Measurements at the level of the sinuses of Valsalva should be indexed for body surface area (9)Mid oesophageal
Long axis
Ascending aorta, 100–120° (2D)Ascending aorta The upper ascending aorta can be imaged by withdrawing the probe slightly and reducing the multiplane angle
The right pulmonary artery is in the near fieldMid oesophageal
Short axis
Ascending aorta, 0° (2D)Withdrawal of the probe will image the ascending aorta in short axis above the leaflets of the AV
The main pulmonary artery is on the rightMid oesophageal
Descending thoracic aorta, 0° (2D)Descending thoracic aorta The entire thoracic aorta can be assessed by withdrawing the probe. Abnormalities can be annotated at a level corresponding with the distance from the incisors as marked on the probe Mid oesophageal
Descending thoracic aorta, 90° (2D)Descending thoracic aorta Atheromatous plaque is often well seen in the long axis view Upper oesophagus
Aortic arch, 0° (2D)The upper oesophageal views are often poorly tolerated by the patient. The probe is turned to the right to keep the aorta in view. The proximal arch is to the left with the distal arch to the right This will hopefully promote a systematic approach to TOE, which is critical not only for education and training, but also when reviewing studies performed by different operators or in different hospital sites.
It is recognised that not all views may be possible in patients and in particular there are certain views that are sometimes poorly tolerated e.g. deep transgastric, upper oesophageal. The decision to omit various views must therefore be made by the operator taking into account the balance between the risks of inadequate data vs patient safety and comfort.
2. Patient safety
TOE is semi-invasive with the potential for serious albeit rare complications. The indications, risks, and precautions for TOE have been described previously (1), (2). It is mandatory to have a routine checklist for certain conditions and problems that may either contraindicate the study or be a cause for concern; e.g., oesophageal stricture, previous gastro-oesophageal surgery, and loose teeth/dentures. This checklist should be documented, preferably in a specific transoesophageal document/care-plan within the medical notes. The British Society of Echocardiography (BSE) and the Association of Cardiothoracic Anaesthetists (ACTA) have produced a checklist that may be used for this purpose (3).
Conscious sedation is used in many units as a routine to facilitate TOE. Only individuals trained in the use of such techniques should administer sedative drugs. Continuous monitoring of oxygen saturations during and after the procedure is mandatory with full resuscitation equipment being readily available. The BSE has produced guidance for the safe use of sedation (10).
Echo labs should have written protocols for the decontamination of probes and sterility of the procedure room. These protocols can be based on the BSE guidance for probe decontamination but should be agreed by the local trust and infection control departments (11).
3. Identifying information
Patient name.
A second unique identifier such as hospital number or date of birth.
Identification of the operator; e.g., initials.
4. Electrocardiogram
An electrocardiogram should be attached ensuring good tracings to facilitate the acquisition of complete digital loops.
5. Intraoperative TOE
Intraoperative TOE is now a well-established procedure that may involve cardiologists, cardiothoracic anaesthetists or cardiac physiologists. It is strongly recommended that such studies follow precisely the same format as a TOE performed in different settings; e.g., a diagnostic study in cardiology outpatients. This approach has a sound medico-legal justification and minimises the risk of missing important diagnoses that may not be apparent on the preoperative transthoracic echocardiogram (TTE). With this in mind, this document has been prepared with the direct involvement of the ACTA and its representatives Justiaan Swanevelder, David Duthie, Donna Greenhalgh, Niall O'Keeffe, and Nick Fletcher.
To that end, intraoperative TOE needs to be well coordinated in order to allow time for a complete study. It is desirable to obtain most of the data before the chest/pericardium is open as this may affect the images; e.g., dimensions of the tricuspid annulus.
The clinician must be aware that the physiology of the patient may be significantly different during intraoperative TOE due to the effects of general anaesthesia, fluid status, or vasoactive drugs. This is an important principle in deciding whether the TOE data should be obtained before the patient is listed for surgery. The most widely quoted example is in the assessment of the severity of mitral regurgitation, which may be misinterpreted depending on the physiology at the time of the study.
6. Duration
It is recommended that 45–60 min is allowed for each TOE. This includes preparation of the patient, e.g., cannulation, consent etc., and may also include a pre-procedure TTE. This should be done in accordance with the BSE guidelines for TTE (4). However it is recognised that certain clinical circumstances may necessitate a more focused approach to the image acquisition but this is a clinical judgement.
7. Reporting
All studies should be completed by issuing a formal report that is documented within the patient's medical records. Ideally this should be in the form of a standardised computerised report available on all contemporary echo systems. The TOE images should be stored in a format that is reliable and easy to access for review. It is recommended that this take the form of digital storage with regular server back up.
8. Measurements
This document indicates several measurements that can be made during a routine TOE. However, it is expected that the vast majority of patients will have already have had TTE. There is a more extensive evidence base for TTE measurements and therefore these should be used where possible.
Some TOE measurements are difficult to perform due to proximity of the transducer; e.g., left atrial (LA) dimensions. Some measurements may be prone to error if off-axis images have been obtained, e.g., left ventricular dimensions.
However, certain measurements, e.g. annular dimensions or aortic root size, are usually more precise on TOE.
Abbreviations
2D | Two-dimensional |
A1, A2, A3 | Scallops of anterior mitral valve leaflet |
ASD | Atrial septal defect |
AV | Aortic valve |
CFM | Colour flow Doppler |
CW | Continuous wave Doppler |
ECG | Electrocardiogram |
IAS | Interatrial septum |
IVC | Inferior vena cava |
IVSd/s | Inter ventricular septal dimension in diastole and systole |
LA | Left atrium |
LAA | Left atrial appendage |
LLPV | Left lower pulmonary vein |
LUPV | Left upper pulmonary vein |
LV | Left ventricle |
LVDd/s | Left ventricular diameter in diastole and systole |
LVOT | Left ventricular outflow tract |
MR | Mitral regurgitation |
NCC | Non coronary cusp |
P1, P2, P3 | Scallops of posterior mitral valve leaflet |
PA | Pulmonary artery |
PFO | Patent foramen ovale |
PW | Pulse wave Doppler |
RA | Right atrium |
RCC | Right coronary cusp |
RLPV | Right lower pulmonary vein |
RUPV | Right upper pulmonary vein |
RV | Right ventricle |
RVd | Right ventricular cavity diameter in diastole |
RVSP | Right ventricular systolic pressure |
SVC | Superior vena cava |
TOE | Transoesophageal echocardiography |
TR | Tricuspid regurgitation |
TTE | Transthoracic echocardiogram |
Declaration of interest
This manuscript was prepared by the British Society of Echocardiography Education Committee. The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of this guideline.
Funding
This guideline did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.
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R Wheeler is the lead author
R Steeds is the Guidelines Chair