Non Invasive Tests
There are various tests that can be used by the cardiac team to diagnose or monitor heart problems. Some such as cardiac catheterisation are invasive (meaning 'entering' the body) and are generally done under general anaesthetic only where it is necessary to acquire more information than has been possible from other methods.
In most instances it is possible to get a clear idea of the exact nature of the heart defect using a series of other tests which are painless and non invasive. Any of the following tests may be routinely used during hospitalisation or at outpatient clinics to assist the doctors with diagnosis and treatment.
A chest x-ray shows the size and position of the heart and can also give assessment on blood flow through the lungs. It is a painless procedure and provided that the patient remains still, only takes a short time. Babies will usually lie on a bed in the radiographers room whilst a parent holds them to keep them still. For this it is necessary for the parent to wear a heavy protective lead apron, which will be supplied in the department. Older children can stand or kneel on a chair in an upright position in front of the screen to have the x ray "picture" taken.
The heart is basically a pump which is used to circulate blood around the body; it does this by contraction (tightening) of the heart muscle which 'squeezes' the blood out of the collecting chambers situated at the bottom. Contractions are triggered by small electrical impulses which occur within the heart and regulate the pumping according to the needs of the body.
The electrical activity of the heart can be monitored by placing sticky conductive patches onto the arms, legs and chest and attaching wires to these which link to a machine which produces a paper printout of the different signals. From this the doctor is able to obtain information about the rhythm of the heart, the size of the four different heart chambers and if any of them are having to work extra hard.
The examination is simple and painless and generally takes about 5-10 minutes to perform.
24 Hour Electrocardiogram
As described above, the electrocardiogram is a quick and simple test, but there are a few occasions where monitoring over such a short period of time will not provide sufficient information, particularly with rhythm problems which can occur intermittently. In this case a patient may be fitted with a monitoring device which uses a small cassette recorder to record every heartbeat over a 24 hour period. It is generally worn around the neck and attached by wires to three sticky patches on the chest, so it is not restrictive in any way and can easily be worn at home.
At the end of the monitoring period the patient returns to the hospital and the information is downloaded from the cassette and played back on a screen where it can be analysed by the doctor.
Echocardiogram (Ultrasound Scan or Echo)
This test uses high-pitched sound waves to look at the structure of the heart and assess its performance - it is completely painless. The patient lies on a bed and after putting a small amount of gel on the end of the transducer (which generates these sound waves), it is placed on the chest and moved around gently. The sound waves are reflected back to the probe and a computer link displays the information as images of the moving heart, valves and blood vessels on a screen where they can be measured and recorded for later reference.
Echo is often combined with Doppler ultrasound and colour Doppler which magnifies the blood flow sounds within the heart, and is used to evaluate the blood flow across the heart's valves.
An echocardiogram takes between 15 minutes and one hour depending on the complexity of the problem. If it is a long procedure a child may get restless and it may be necessary for them to take a mild sedative as it is essential that they keep still, although a favourite toy or story may be helpful for many children. Babies sometimes fall asleep.
Transoesophageal echocardiogram (TOE)
This test is very useful in patients where adequate images cannot be obtained using normal echocardiography. It requires the transducer to be inserted down the throat into the oesophagus (the tube from the mouth to the stomach) and can provide good images as the sound waves do not have to pass through the chest wall or the lungs.
The patient is sedated for the procedure and the back of the throat is sprayed with an anaesthetic spray to suppress the gag reflex, then the probe is introduced via the mouth. The test takes about 90 minutes to perform and when it is complete the tube is withdrawn - it takes about an hour for the anaesthetic spray to wear off before they can eat and drink.
This is a form of x-ray, where the patient lies down, usually sedated or fully asleep (anaesthetised) on a special bed. The bed slides into a short tunnel and then the x-rays can be taken. They build up pictures or slices of the heart, blood vessels and chest. The pictures are then processed with fast computers to give the doctors clear and detailed images.
Like a CT scan, the patient lies down, usually sedated or fully asleep (anaesthetised) on a special bed. However, this test does not use any x-rays, and gives different details on the structures within the body. It can be used for building up 3-D pictures or slices of the heart in the same way as a CT scan, but is more detailed. It is also good at looking at the function of the heart and the blood flow to the different body organs.
This machine uses an infra red beam to measure the percentage of oxygen in the blood, which provides one indication of how efficiently the heart is working. It uses a probe which is similar to a "clothes peg" placed on the finger, ear lobe or toe, and can have an alarm which sounds if oxygen levels fall below a set figure. Readings from the pulse oximeter are often referred to as 'sats' which is an abbreviation of Oxygen Saturation levels.