Heart ECG machine: what should you know?

An ECG machine detects tiny electrical changes each time the heart beats and displays them as a tracing. It does not send electricity into your body. The tracing can give clues about an irregular rhythm, a fast or slow rate, or changes that need further evaluation. It is a snapshot, so an intermittent problem may not appear during a brief recording.

During a standard ECG, electrodes are placed on the chest and limbs while you lie still. The process is usually brief. Loose clothing, body hair, skin products, movement, or a poor electrode connection can affect the recording, so the clinician may prepare the skin or repeat a lead.

Wear clothing that allows access to your chest and limbs, and tell the clinician about symptoms, medicines, implanted devices, or skin sensitivity. Follow the appointment instructions and try to relax while the tracing is recorded. Bring details of when palpitations, chest discomfort, dizziness, or breathlessness occur. Ask whether you need a resting ECG, an exercise test, or longer monitoring.

Do not wait for a routine ECG appointment if you have chest pressure, severe breathlessness, fainting, sudden weakness, or a sustained racing or irregular heartbeat with dizziness. Seek emergency help. An ECG result should be interpreted with your symptoms and examination; an apparently reassuring tracing does not make severe symptoms safe to ignore.

Why has an ECG been suggested? Was the tracing clear, and what does it show alongside my symptoms? Could longer monitoring or another test provide useful information?