An ECG test, also known as an electrocardiogram, is one of the most commonly used investigations in cardiology. Many patients are referred for an ECG as part of an initial assessment, either because they have symptoms or as part of a routine review. Although the test itself is straightforward, it is natural to have questions about what it involves and what information it provides.
An ECG records the electrical activity of the heart. It does not involve needles, injections, or radiation, and it is usually completed within a few minutes.
Why an ECG test is performed
The heart beats as a result of electrical signals that travel through the heart muscle in a coordinated way. An ECG provides a snapshot of this electrical activity at a single point in time.
An ECG test may be requested for several reasons, including:
- chest pain or chest discomfort
- palpitations or awareness of the heartbeat
- breathlessness
- dizziness or blackouts
- monitoring known heart conditions
- routine assessment in patients with cardiac risk factors
The test can help identify heart rhythm problems, evidence of previous heart damage, and signs that suggest strain on the heart.
What happens during an ECG test
An ECG is usually carried out while you are lying down and resting. You will be asked to remove clothing from the upper body so that small sticky pads, called electrodes, can be placed on the chest, arms, and legs.
These electrodes are connected to the ECG machine by wires. The machine records the heart’s electrical signals and produces a trace, which is displayed on a screen or printed on paper.
The test itself is painless. You do not feel the electrical signals being recorded, and nothing is sent into the body. You will be asked to remain still and breathe normally while the recording is taken, which usually lasts only a few seconds.
Once the recording is complete, the electrodes are removed and you can get dressed straight away.
Do you need to prepare for an ECG?
In most cases, no special preparation is required. You can eat, drink, and take your usual medications unless you have been advised otherwise.
It is helpful to wear clothing that allows easy access to the chest. If you have a very hairy chest, some hair may need to be trimmed to allow the electrodes to stick properly, but this is usually minimal.
You should let the clinician know if you have any symptoms at the time of the test, or if you have experienced symptoms recently, even if they are not present during the ECG.
What an ECG test can show
An ECG provides valuable information, but it is important to understand what it can and cannot detect.
An ECG can show:
- abnormal heart rhythms, such as atrial fibrillation
- slow or fast heart rates
- signs of previous heart attacks
- conduction problems affecting how electrical signals travel through the heart
- patterns that suggest strain on the heart or certain structural conditions
These findings help guide further investigation or treatment when needed.
What an ECG test cannot show
A normal ECG does not rule out all heart problems. This is an important point for patients to understand.
An ECG records the heart’s electrical activity at the moment the test is taken. If symptoms are intermittent, such as occasional palpitations, the ECG may appear normal if the symptom is not present at the time.
An ECG also does not directly show the structure of the heart or how well the heart muscle and valves are functioning. For this reason, further tests such as an echocardiogram or ECG monitoring may be recommended depending on the clinical context.
ECG tests and symptoms
When symptoms such as palpitations, chest pain, or dizziness are present, an ECG is often the first investigation. It can provide immediate information that helps narrow down possible causes.
For example, palpitations may be due to a rhythm disturbance that is visible on the ECG. However, many palpitations are benign and may not be captured on a single ECG. In these cases, longer term monitoring using a wearable ECG recorder may be more helpful.
Similarly, chest pain is not always due to heart disease, and the ECG helps determine whether there are signs that suggest reduced blood flow to the heart muscle or previous damage.
Exercise ECGs and other ECG based tests
A standard ECG is performed at rest. In some situations, an exercise ECG may be recommended. This involves recording the ECG while you walk on a treadmill or pedal a stationary bike.
An exercise ECG can help assess how the heart responds to physical stress and whether symptoms or ECG changes occur during exertion. It is often used when symptoms are exercise related.
Other forms of ECG monitoring include 24 hour or longer recordings, which are useful when symptoms occur sporadically.
How ECG results are interpreted
ECG traces are interpreted by trained clinicians who consider the pattern of the electrical signals alongside symptoms, examination findings, and other test results.
An abnormal ECG does not always mean that there is a serious problem. Some changes are common and harmless, particularly in healthy individuals or athletes. Equally, a normal ECG does not always exclude heart disease.
This is why ECG results are always interpreted in context rather than in isolation.
After the ECG test
In many cases, the results of an ECG can be discussed shortly after the test. If further investigation is needed, this will be explained and arranged as appropriate.
If the ECG is reassuring and symptoms are mild or non specific, no further testing may be required. In the case abnormalities are found, additional tests may be recommended to clarify the cause and guide management.
When to seek further advice
It is sensible to seek assessment if you experience ongoing or worsening symptoms such as chest pain, breathlessness, palpitations, dizziness, or blackouts. An ECG is often the first step in understanding these symptoms, but it is rarely the final answer on its own.
If you would like to discuss whether an ECG test is appropriate for you, or to talk through the results of a test you have already had, you can get in touch with me to arrange a consultation and review your symptoms in context.
But to summarise an ECG test is a simple but valuable tool. When used appropriately and interpreted carefully, it plays an important role in understanding heart symptoms and guiding further assessment in a calm and structured way.