It is usually done to look at particular parts of the heart that are less well seen on the standard (trans-thoracic) echo scans that you have in the clinic. Parts of the heart that are particularly well seen on TOE include the atriums and the heart valves.

TOE is done to look for various things, but the more common reasons would be atrial septal defects, problems with the heart valves (for example leaky valves) or heart infections (endocarditis).

It will usually be done in hospital. This can often be your local hospital, but for rarer or more complex situations you may need to go to Auckland.

The TOE will be done by a cardiologist who has special training and expertise in performing this procedure.

Not usually. The TOE can usually be done with some sedation medicine. Commonly used medicines include fentanyl and midazolam: these make you drowsy and relaxed, and also mean that you don’t remember the procedure.

You will be given the sedation medicine through an intravenous line that has been put into a vein in your arm. An anaesthetic spray is then used to make your tongue and throat feel numb. It may taste bitter. You will lie on your left side for the procedure. A mouthguard will protect your teeth.

The ultrasound probe that acquires the TOE pictures is a long thin tube that you swallow. It passes down your throat into your oesophagus (the tube that takes food from your mouth to your stomach). The probe is always sterilised between scans.

The probe is attached to the ultrasound scanning machine. From inside your oesophagus and stomach the probe will produce clear pictures of your heart. The doctor will make small movements of the probe in order to get all the different pictures that are required. Once the pictures have been obtained, the probe will be taken out. The TOE usually takes about 20-30 minutes.

The picture shows a TOE probe being used in a training dummy. The probe usually measures between about 10-16 mm in diameter. This is no thicker than many foods you swallow.

The risk of major complications is low.

The most common thing that people notice is a sore throat for a couple of days after the TOE is done.

More major complications are rare, but include bleeding or other injury to the mouth, osophagus or stomach. Breathing problems, heart rhythm changes and infection are also rare complications. The cardiologist will talk to you about this in more detail before you give your consent to have the test.

Sometimes a TOE cannot be done if you have other medical conditions that cause problems with your oesophagus or stomach.

Let your doctor know before the TOE if you have had any previous surgery to your stomach or oesophagus. Also let the team know if you have difficulty swallowing, or you have any other stomach or oesophagus problems.

You should let the team know if your are taking an anti-coagulant (blood thinning) medicine, as you may sometimes need to stop this medicine before the TOE is done.

On the day of the procedure you’ll usually be asked not to eat or drink anything for a few hours beforehand – the exact timing will be specified on the information that you are given prior to the TOE.

The other thing that you will need to think about is how you will get home after the TOE. Because of the sedation medicine you will not be able to drive for the rest of the day, so someone else will need to drive you home or you could take a taxi or public transport.

You should expect to be in the hospital for at least 2 hours in total.