ECG
A recording of the electrical activity of the heart, taken through electrodes on the skin.
What it means
An ECG records the electrical signals that coordinate each heartbeat, picked up by electrodes on the chest and limbs. It is painless, takes minutes, and involves no radiation.
It shows the heart rhythm, evidence of previous heart attacks, thickening of the heart muscle, and some effects of medicines and electrolyte disturbances.
What it does not show is the coronary arteries — they are not visible on an ECG. This is the single most important limitation to understand.
In practice
A Holter monitor records over 24 hours or longer, catching intermittent rhythm problems a resting ECG misses. An exercise ECG records during exertion.
An ECG is a snapshot: a normal one taken between episodes of palpitations tells you nothing about what happens during them.
Why it matters
A normal ECG does not rule out a heart attack. A significant proportion of heart attacks show a normal or near-normal ECG initially, which is why blood troponin tests and repeat tracings are done. Never let a normal ECG reassure you out of ongoing chest pain — call 999.
ECG is not part of a remote consultation. We would arrange one locally or direct to urgent care where the story warrants it.
Clinically reviewed by Dr Mohammad Zubair Khan, GMC 7563469
Last reviewed
August 30, 2026