What should you know about an electrocardiogram?

The tracing helps a clinician assess heart rate, rhythm, and the timing of electrical activity. It can support assessment of palpitations, chest discomfort, breathlessness, fainting, or an irregular pulse. An ECG may provide clues associated with angina, atrial fibrillation, or heart failure, but it is only one part of an assessment. A normal tracing does not explain every symptom, and an unusual tracing does not by itself establish a complete diagnosis.

Wear clothing that allows access to the chest, arms, and ankles, and tell the clinician about medicines or implanted devices. You usually lie still while the ECG machine captures the tracing; the stickers may feel cool and their removal can briefly tug body hair. Avoid talking or moving during recording because muscle activity can interfere with the signal. Ask when and how the result will be explained, especially if the ECG was done for a new symptom.

Call emergency services for chest pressure or pain that is severe, persistent, or spreading to the arm, jaw, back, or shoulder, especially with sweating, nausea, fainting, or breathlessness. Seek urgent help for collapse, severe breathing difficulty, or a new fast or irregular heartbeat with dizziness. Do not wait for a routine ECG appointment when these symptoms are present.

Ask why the ECG is recommended, whether you need monitoring beyond a brief tracing, what the result means in context, and which symptoms should trigger urgent review.