Echocardiography: transthoracic and transoesophageal

What it is

Echocardiography uses ultrasound to show the heart in motion without radiation. In transthoracic echocardiography (TTE) a probe with gel is placed on the chest at standard windows (parasternal, apical, subcostal and suprasternal) with the patient lying on the left side; it takes a short time, needs no preparation and can be repeated at the bedside. Two-dimensional images show the size and wall motion of the chambers, the thickness of the walls, the valves and the pericardium; Doppler measures the speed and direction of blood flow. From these speeds the machine calculates pressure gradients with the simplified Bernoulli equation (gradient = 4 × velocity²), valve areas with the continuity equation, cardiac output, and the pulmonary artery systolic pressure from the tricuspid regurgitation jet plus the estimated right atrial pressure. The left ventricular ejection fraction (LVEF) classifies heart failure. Transoesophageal echocardiography (TOE) places the probe in the oesophagus, directly behind the left atrium, under sedation and throat anaesthesia: it gives much clearer images of the atria, the left atrial appendage, the mitral and prosthetic valves and the thoracic aorta, at the cost of fasting, sedation and small procedural risks. Stress echocardiography, contrast echo and the agitated-saline bubble study extend both.

Indications

• Heart failure, breathlessness or oedema of possible cardiac origin: ventricular size and function.
• A new murmur, suspected valve disease or prosthetic valve follow-up.
• Suspected endocarditis: TTE first; TOE if TTE is negative with high suspicion, with a prosthetic valve or suspected abscess.
• After myocardial infarction: wall motion, ejection fraction and mechanical complications; suspected pericardial effusion or tamponade.
• Atrial fibrillation, stroke or embolism of possible cardiac source (TOE and bubble study for appendage thrombus or shunt); pulmonary hypertension.

Contraindications

• TTE: no contraindications; chest wounds, dressings, obesity or lung disease only limit the image windows.
• TOE absolute: oesophageal stricture, tumour, perforation or recent oesophageal or gastric surgery; active upper GI bleeding.
• TOE relative: oesophageal varices, previous neck or chest radiotherapy, unstable cervical spine, severe coagulopathy, dysphagia.
• TOE needs a protected airway and a patient fit for sedation; not fasted, uncooperative or hypoxic patients need a different plan.
• Stress echo: the same contraindications as other stress tests (unstable coronary syndrome, severe symptomatic aortic stenosis).

Preparation and what happens

1. State the question on the request (ejection fraction, valve, vegetation, effusion) — the echo is tailored to it and read in context.
2. TTE: the patient undresses to the waist and lies on the left side; no fasting — the left lateral position brings the heart to the chest wall.
3. Electrodes give a rhythm trace and gel is applied under the probe — timing and good contact improve the measurements.
4. TOE: explain, obtain written consent, and ask about swallowing problems, oesophageal disease, bleeding and loose teeth — these change the risk.
5. TOE: fasting for several hours, dentures removed, cannula placed — an empty stomach reduces aspiration under sedation.
6. TOE: throat spray and light sedation are given, with oxygen saturation, blood pressure and ECG monitored — the probe is then swallowed.
7. Images are taken from several depths and angles, with colour and spectral Doppler — each view answers part of the question.
8. After TOE: nothing by mouth until the throat numbness wears off; an escort home after sedation — the cough reflex is blunted.

Common echo measurements in adults (cut-offs vary slightly between guidelines and laboratories)

Risks and complications

• TTE: no known harm; poor windows can give an incomplete or misleading study.
• TOE: sore throat, minor bleeding and transient hoarseness are the common complaints.
• TOE sedation: hypoxia, hypotension, aspiration and laryngospasm; monitoring and a recovery area are needed.
• TOE rare but serious: oesophageal or pharyngeal perforation, dental injury, and methaemoglobinaemia from the local anaesthetic throat spray.
• Errors of reading: a normal ejection fraction does not exclude heart failure with preserved ejection fraction; a negative TTE does not exclude endocarditis.

Next step

• Act on urgent findings at once and call a senior: tamponade, a large vegetation, aortic dissection, a mechanical complication of infarction.
• Reduced ejection fraction: start or adjust heart-failure treatment and plan follow-up imaging.
• Valve disease: grade it, follow it with repeat echocardiography at intervals set by severity, and refer severe symptomatic disease to cardiology.
• Negative TTE with high suspicion of endocarditis or a cardiac source of embolism: request TOE.
• After TOE: check that the patient can swallow before eating; ask about chest or neck pain, fever or worsening throat pain in the next days (perforation).

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Elsewhere in DurgiPedia

• The cardiac cycle
• The ventricular pressure–volume loop
• Heart failure physiology
• Murmurs: timing, grade, location and radiation
• Cardiomegaly and pulmonary oedema on the chest X-ray

Connections

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Educational content; it does not replace supervised hands-on training, your institution's protocols or a prescriber's order. A procedure is learnt with a teacher and done only once you are trained to do it.

Sources: Basic Concepts of Echocardiography Hemodynamics (StatPearls (NCBI Bookshelf), 2022).

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Representative model, for educational purposes only.