A transoesophageal echocardiogram (TOE) is an ultrasound scan of the heart, which involves sending an ultrasound probe at the end of a flexible tube called an endoscope down the oesophagus (gullet) to take high quality pictures of the heart.
The heart is only about a centimetre away from the gullet, hence a TOE probe can see structures of the heart much more clearly than pictures taken from the front of the heart through the chest and ribcage.
Patients having the test are given a local anaesthetic spray to the throat, followed by a light sedation. You are normally asked not to eat or drink anything for six hours before the procedure, although you can take your usual heart tablets if necessary with a very small amount of water.
After consent is obtained, the patient is asked to lie on their left side, and the probe is gently passed into the gullet. Once the probe is advanced into the gullet, high quality 3D and 4D images (i.e. taken live so they include a time factor) are obtained of the heart valves and function, allowing a consultant to plan surgery. The test takes approximately 20 minutes.
The test is particularly useful for patients with mitral valve disease – an irregularity in the valve between the two chambers on the left-hand side of the heart – and those with holes between chambers of the heart which cannot normally be seen well from the front of the heart.
It's an extremely useful test to look for blood clots in the top left chamber of the heart (left atrial appendage) which cannot be seen by ultrasound from the front of the chest.
Patients are monitored in recovery for an hour at the end of the procedure, and then discharged home with someone accompanying them.
Due to sedation, you will be advised not to drive for the rest of the day and not to have any hot or very cold drinks or food for two hours after the procedure, as you will not feel the temperature sensations in your throat.
There are some minor potential side effects to having the procedure. One in 100 patients could experience a sore throat for the first 24 hours.
There's a 1 in 1000 chance the probe could cause minor cuts, bruises or minor bleeding at the back of the throat, tongue or damage the teeth. Precautions are taken to avoid the latter by using a mouth guard.
In very rare circumstances, sedation may make a patient very drowsy, slowing breathing, leading to a reduction in oxygen levels in the blood, and then the patient will require reversal of sedation and a high flow of oxygen.
The main limitation of the TOE is that around 5% of patients may not be able to take the probe easily into their gullet and the procedure has to be abandoned or rescheduled.
This may be due to anatomical anomalies – some patients may have a pouch in their upper oesophagus that the probe may be inadvertently going into – or simply because patients may be unable to tolerate and swallow the probe.