We will refer to the above picture again and again as we view the heart using TOE. Note that in the picture the "fan" of ultrasound is cutting the heart obliquely, and not at 90^o to the long axis of the heart. This is a common problem, and if not corrected it will give you misleading information about ventricular contractility and wall motion. Beware!

A few practical tips (Thanks to Dr Olaf Larson for highlighting these!):

1. Right heart structures occupy most of the anterior aspect of the heart, with the right ventricular outflow tract arising anteriorly and passing almost horizontally back;
2. Conversely, left heart structures are mostly posterior, with the LVOT arising posteriorly and moving up, anteriorly and to the right;
3. From above down, the order of the heart valves is (a) pulmonary, (b) aortic, (c) mitral, and lastly (d) the tricuspid. These valves provide invaluable clues as to where you are! Of these, perhaps the most characteristic is the..
4. Aortic valve, with its "Mercedes Benz" sign, and the non-coronary cusp adjacent to the inter-atrial septum
5. The anterior mitral leaflet is longer and more medial than the posterior leaflet.
6. If you see a circular structure at the apex of the sector image, you're looking at the descending thoracic aorta.

Note that, by convention, the TEE image is displayed with the probe positioned at the top of the screen, and structures on the patient's right are shown on the "screen's right" - your left, as you watch the screen, just as with viewing a normal chest x-ray. {In contrast, the Mayo Clinic has its own peculiarly logical way of doing things}. This is in the "transverse plane", which is conventionally labelled as "0 degrees". If we rotate the plane of scanning "forward" to 90^o, then we will progressively see structures that are more inferiorly located, and these will creep in on the left of the screen. Further rotation forward to 180^o results in a mirror image of the picture seen at zero degrees.

Different strokes..

	A. Transgastric
	B. Mid-oesophageal
	C. Basal

Some authorities lump the last two together as 'Mid-oesophageal', and also talk about 'upper oesophageal' (UE) views when looking at the aorta. At each of these levels, different views can be obtained by manipulating the probe - the controls of the "gastroscope" can be used to flex or extend the tip, allowing various views to be obtained. (Further 'fine-tuning' can be achieved by gently rotating the scope, or advancing or withdrawing it). This document contains representative views at the three levels. Note that one should not have a pseudo-religious fixation about 'levels' and 'planes', especially with the advent of multiplane TOE - rather tailor the examination to allow adequate examination of all structures. Our "three levels" are merely a guideline!

Pitfalls

Note that over or under diagnosis of spontaneous contrast can be compensated for by setting the gain to fairly high contrast, comparing with the pulmonary veins which very infrequently show spontaneous contrast, and noting the swirls which are invariably present with true spontaneous contrast.

For assessment of stenotic lesions, conventional TEE studies are often inadequate, and CW doppler is required, although even this may underestimate the lesions if improperly used.

A. Transgastric views

	1. The LV short axis view at the level of the papillary muscles
	2. The LV short axis mitral view

The transgastric short axis views are mainly used for assessment of left ventricular function and myocardial ischaemia. The most useful view in this regard is the LV short axis view at the level of the papillary muscles.

Pitfalls

If the left atrium and/or right ventricle are markedly enlarged, displacement of the left ventricle may prevent adequate visualisation of the short axis LV.

During intra-operative assessment, lighting is often excessive, compromising visualisation, small bubbles are common and should not be mis-diagnosed as spontaneous contrast, probe manipulation may be difficult, and electrocautery may interfere with the functioning of the echo machine. Adequate ECG lead placement is vital. The probe should be switched off when not in use, as otherwise overheating (and consequent cut-out) is common - some even irrigate the oesophagus with iced saline!

The LV short axis view at the level of the papillary muscles (TG Mid SAX)

The following pictures show (on the right) an echocardiographic image of the LV short axis, and on the left, an anatomical image taken from the visible human project. If you move your mouse over the left image, then the picture should change to a labelled one, with the right (RV) and left (LV) ventricular cavities clearly visible, the interventricular septum (ivs) between, them, and the strangely named inferior, posterior, and anterior walls of the left ventricle shown (iw, pw and aw respectively) together with their blood supply. The territory supplied by the left anterior descending coronary artery is shown in green, that supplied by the circumflex in red, and the right coronary artery territory in blue.

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The papillary muscles are also labelled (pm = posteromedial, al = anterolateral). (If anything, the anatomical section is a bit too close to the mitral valve, and the papillary muscles are thus smaller in cross section - we've taken this section because in sections nearer the apex, the left ventricular cavity is minuscule). In addition, the left ventricle in the visible human is very poorly filled, so the wall appears thickened, and the cavity diminished. Note that coronary anatomy varies considerably from individual to individual, so the above supply doesn't necessarily apply to everyone. Use the information contained in an angiogram of the patient, if you have this!

Obtaining the views

As the probe tip passes through the gastro-oesophageal junction, there may be some patient discomfort. Reassure them, then anteflex the probe to keep mucosal contact. The depth of field needs to be increased to adequately view all structures.

The LV short axis mitral view (TG Basal SAX)

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Again, move your mouse cursor over the left image to reveal the labels. The anterior leaflet of the mitral valve (aml) is clearly seen between the left ventricular outflow tract (lvot) and the mitral valve orifice (mvo).

	1. Four chamber view
	2. "Five chamber" view
	3. Right-ventricular inflow and coronary sinus view
	4. RV inflow/outflow

The mid-oesophageal views have a variety of uses, and are good for assessing the atria, ventricular septum, ventricles, the "internal crux" of the heart, and both AV valves and their supporting structures.

The LVOT is particularly well seen in the apical five-chamber view, especially in assessing "septal hypertrophy" and hypertrophic cardiomyopathy.

(Colour flow doppler of the LVOT is useful in assessing aortic regurgitation, and also mitral flow; steerable CW is great for the jets of MS and MR, as well as AS and AR).

Pitfalls

Prosthetic valves may obscure visualisation of the ventricles.

Four chamber view (ME 4 Chamber)

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In the picture from the visible human slice server on the left, note how dilated the right side of the heart is, with the left side extremely poorly filled (This isn't normal). You can still however still see all four chambers clearly, with the interatrial septum bulging into the left atrium! Three of the chambers are labelled (RA, LA, RV) - but the left ventricle is also clearly identifiable. You can also clearly delineate the mitral valve (mv), tricuspid (tv) and lateral wall of the left ventricle (lw). In the echo image, you can actually also see the start of the LV outflow tract, so technically this is a 'five-chamber' view (see below).

Obtaining the view

This view is usually obtained with the probe 35-37 cm from the incisor teeth. Note that good views of the mitral valve are obtained, and the interatrial septum is also well seen, but the apex of the left ventricle is usually not well seen, precluding assessment of ventricular function.

"Five chamber" view

In the misleadingly named "five-chamber view" (the fifth chamber is the LV outflow tract) all four chambers can again be seen, but so too can the aortic valve (av) and the left ventricular outflow tract (lvot), separated as usual from the left atrium by the anterior leaflet of the mitral valve.

Right-ventricular inflow and coronary sinus view (ME RV Inflow)

In these views, the coronary sinus (cs) is clearly visible, and the inferior vena cava (ivc) can just be seen starting to appear, draining into the right atrium (RA). Note that the coronary sinus runs in a groove between the left ventricle and left atrium, so that if these chambers are well filled (which is not the case in the visible human) then the left atrium may also be visible. (The LA would also be better seen from a vantage point slightly higher up the oesophagus, with the probe beam directed inferiorly and anteriorly, rather than the nearly horizontal cuts shown here). The echo image is greatly enlarged compared with the anatomical one, and in a somewhat different plane! The 'standard' ASE view incorporates the RV outflow, which is not seen in our image.

Right-ventricular inflow/outflow (ME RV Inflow/Outflow)

In the following image, the RV inflow and outflow can be seen, with a pulmonary artery catheter transgressing both!


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	1. Short axis basal (AV, RVOT, atrial septum)
	2. Coronary arteries
	3. Left atrial appendage
	4. Short axis SVC, ascending aorta
	5. Main pulmonary artery
	6. Pulmonary veins

Basal short axis views are good for assessing the anatomy of a variety of structures, including the Aortic Valve, coronary arteries, left atrial appendage, RVOT, SVC, upper pulmonary veins, and pulmonary arteries. (Colour flow Dopper is often a useful adjunct).

Short axis basal (Aortic Valve, RVOT, atrial septum) 'ME AV SAX'

The following view is really rather important, mainly because it contains an unmistakable landmark - the 'Mercedes-Benz sign'of the aortic valve in cross section (av). Posterior to this valve (and close to the probe) you can see the left atrium, to the patient's right (your left) is the right atrium, and ventrally is the right ventricular outflow tract.

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Note that the anatomical section is slightly off-true, so the sign is skewed - a useful tip! Note that in this fairly cephalad view, the interatrial septum is thick - more inferiorly it thins markedly. The right ventricular outflow tract is also well seen (rvot).

Coronary arteries

In the anatomical section, both coronary arteries can be fairly well seen coming off the aorta (Ao), the left (lca) running laterally and the right (rca) in between the pulmonary artery (Pa) and right atrial appendage (raa). The superior vena cava (svc) also now comes into the picture. In the upper TOE picture, only the left coronary artery can be seen, at a slightly greater magnification; in the lower picture, you can see just the RCA.

Left atrial appendage

The left atrial appendage (laa) is well seen in a range of transverse anatomical sections through the visible human - we've chosen one where it's particularly well delineated, but it can even be visualised in the previous (coronary artery) images - can you spot it? Note in our anatomical image the bulky area where the left superior pulmonary vein (lspv) meets the left atrium - to the uninitiated, this can look like thrombus in the left atrium!

Short axis SVC, ascending aorta

We have not illustrated this view, as it is very similar to the following.

Main pulmonary artery (with RPA) - 'ME Asc Aortic SAX'

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These views are of the main pulmonary artery at the level of its bifurcation. See how the origin of the right pulmonary artery is visible (rpa), but note the position of the left main bronchus (lmb) in the image - even if you move cephalad and rotate the probe, to try and visualise the left pulmonary artery, it will be obscured by this bronchus!

Pulmonary veins

[When we have adequate images of these, we'll insert them here!]

The left superior pulmonary vein is fairly well seen in the left atrial appendage view above.

Obtaining the Images