How does an electrocardiogram work?

During an ECG, small adhesive electrodes are placed on the chest and usually the limbs. Wires connect them to an ECG Machine, which records different views of the same electrical activity. The tracing can help a clinician assess heart rate, rhythm, conduction and some patterns linked with reduced blood supply or a previous injury.

A resting ECG is recorded while you lie still. Other versions record activity for longer or during exertion when symptoms come and go. An ECG supports assessment of concerns such as Atrial Fibrillation, Angina or a Heart Attack, but a normal tracing does not explain every type of chest symptom.

Wear clothing that allows access to the chest and lower limbs, and avoid creams or oils on electrode areas if possible. Tell the clinician about medicines, implanted devices and symptoms such as palpitations, dizziness or chest discomfort. Keep still and breathe normally while the recording is made; movement can add interference.

The test does not send electricity into your body. Your clinician interprets the tracing alongside your symptoms, examination and other tests. If the result needs context, a GP Consultation may be the next step.

Call emergency services for chest pressure or pain that is severe, persistent or spreading to the arm, jaw or back, especially with breathlessness, sweating, faintness or nausea. Do not wait for a routine ECG when these symptoms are happening. New fainting, severe breathlessness or a sustained fast or irregular heartbeat also needs urgent assessment.

Ask why the ECG is recommended, whether you need a resting or longer recording, and when the result will be reviewed. If symptoms were absent during the test, ask whether another form of monitoring could be useful.