Glossary term · Tests & reports
Electrocardiogram (ECG) (also: ECG, EKG, 12-lead ECG): An electrocardiogram is a painless test that records the heart’s electrical activity through small electrodes placed on the chest, arms and legs.
An electrocardiogram, or ECG, records the electrical activity of your heart. MedlinePlus says it is often the first test used to check for heart disease. It shows how fast the heart beats and whether the rhythm is steady. It is quick and painless. MedlinePlus lists it among the common checks before surgery, even when the operation is not on the heart.
How is an ECG done?
You lie down while small sticky patches called electrodes are placed on your arms, legs and chest. You need to stay still and relaxed, because movement or shivering can alter the results. Sometimes the ECG is recorded during exercise, which is called a stress test.
What does it show?
- Heart rate and rhythm.
- Signs of heart damage.
- Effects of heart medicines or devices such as pacemakers.
- The size and position of the heart chambers.
What are its limits?
MedlinePlus notes that some heart conditions never produce specific ECG changes. A normal ECG does not rule out heart disease. Your cardiologist may add an echocardiogram or other tests.
Why is it done before surgery?
MedlinePlus lists an ECG among the common checks before surgery, alongside blood tests and sometimes a chest X-ray. It helps the anaesthesia team assess your heart.
Before the test
Tell the team about all your medicines. MedlinePlus advises avoiding exercise or cold water just before the test, as these can affect results.
Questions people ask
Should I send my old ECGs?
Yes, especially if you have a known heart condition. A comparison with earlier tracings can help the cardiologist see changes. Scan the full tracing clearly rather than sending only the printed interpretation.
Does an ECG hurt?
No. MedlinePlus describes the test as painless, though the electrodes may feel cold at first. Rarely, a rash or irritation develops where the patches were placed. It carries no known risks.
Sources
- MedlinePlus: Electrocardiogram
- MedlinePlus: Heart health tests
- MedlinePlus: Tests and visits before surgery
General information, not medical or legal advice. Rules change: confirm with the official source. Your treating specialist decides on suitability, treatment and length of stay. How we write and check.