Detailed ultrasound imaging of cardiac structures using an endoscope

TOE vs. TTE (transthoracic echo)

TOE is a detailed ultrasound assessment of the heart using a special endoscope (a flexible tube) with an ultrasound transducer which produces ultrasound waves. The probe is passed through your mouth into the oesophagus (food pipe) just behind the heart. The word 'trans-oesophageal' means 'through the oesophagus'. The transducer sends ultrasound into the heart and then receives the echo, i.e. the signals that bounce back. The signals are transformed into pictures that show on a screen.

Transesophageal echocardiography (TOE) is used if the transthoracic echocardiogram (TTE) doesn’t produce clear results. Compared with transthoracic echo, TOE provides clearer and sharper images because the distance from the probe to the heart is much shorter and the ultrasound waves don’t have to pass through the chest wall and lungs. TOE is superior to TTE in evaluation of heart valves, both atria (top heart chambers), atrial septum, left atrial appendage (a muscular pouch connected to the left atrium where blood clots can sometimes be found in atrial fibrillation), aorta and pulmonary artery. TOE also has some disadvantages; it may be uncomfortable, usually requires mild sedation (medicine to help you relax, e.g. Midazolam) and as semi-invasive test, it has a small but finite risk of complications.

TOE is usually a one-off procedure; if echo follow-up is necessary, standard transthoracic (surface) echo is normally sufficient.

Indications

• Poor image quality with transthoracic echocardiography
• Detailed assessment of heart valves, especially prosthetic (artificial) valves
• Suspicion on infective endocarditis (infection affecting heart valves)
• Detection of thrombus (blood clot) within the heart prior to cardioversion (jump-starting the heart with electric shock, e.g. in atrial fibrillation)
• Investigation of possible cardiac sources of emboli (dislodged blood clots)
• Evaluation of atrial septum, atrial septal defect (‘hole’ in the heart) and atrial septum aneurysm (floppy septum)
• Investigation of cardiac masses
• Evaluation of aorta, presence and severity of aortic atheroma / atherosclerosis (thickening of wall of the vessel) and aortic dissection (medical emergency with partial rupture of the aortic wall)
• Intraoperative monitoring in cardiac surgery to assess adequacy of valve repair
  
  

Risks and complications

Transoesophageal echocardiography is a very safe procedure. Dr Ruzicka will explain possible risks in detail and you will be asked to sign informed consent. The complications involve soreness in the mouth and throat due to manipulation with the probe, damage to teeth (with plastic mouth guard in place, the risk is minimal), perforation of the oesophagus (risk is about 1:10,000) and somnolence from sedation.

Before the procedure

Do not eat or drink anything from midnight before your appointment. Please do not stop any medication, particularly anticoagulants (warfarin, apixaban, edoxaban, rivaroxaban, dabigatran). You can drink water, clear tea and black coffee (without milk) up to 2 hours before the procedure. Milk, food, sweets, tea or coffee with milk can be consumed up to 6 hours before the procedure. Chewing gum and smoking is not permitted on day of the test. Please bring the list of your medication with you. If you are diabetic, please do not take your diabetic medication but bring it along with some food with you so you can have it after the investigation is completed. You will be asked to remove any full or partial dentures. Dr Ruzicka will explain the test to you and any questions you may have can be answered prior to signing the consent form. A small needle will be put in your arm. Three  ECG electrodes (plastic stickers) will be placed on your right side, left and right shoulder and attached with leads to the echo machine.

During the procedure

Anaesthetic spray (e.g. Xylocain spray) will be used to numb the throat and usually a small dose of sedation (medicine to help you relax, e.g. Midazolam) will be given. A saturation probe and blood pressure cuff will be attached to monitor the level of oxygen in the blood and blood pressure. The probe with lubricant will then be put on your tongue and you will be asked to swallow the probe which will be gently introduced to the gullet (= oesophagus). If necessary, the sedation can be titrated up during the procedure. Oxygen mask may be given to help with breathing. The difficult part of the test is the swallowing of the probe but once it is down in the oesophagus, the procedure becomes much more comfortable. Because of the position of the probe, you will not be able to talk during the test. The procedure takes approximately 20-30 minutes.

After the procedure

It can take up to 30 minutes for full feeling in your throat to return. You will then be able to eat and drink normally. You will remain in the department for 1-2 hours and have some refreshment. Before you are discharged, Dr Ruzicka will shortly talk to you about the result of the test and any follow-up arrangements. Because of the sedation, it is best to discuss the results in detail in a separate session and have someone to pick you up from the clinic and stay with you for the rest of the day.

If sedation is administered, it can remain in your system for 24 hours, you should until then:
   - Have someone to take you home and stay with you
   - Not drive (you will not be covered by insurance)
   - Not return to work
   - Not operate any kind of machinery, including domestic appliances
   - Not drink alcohol
   - Not sign any important or legal documents