An ECG is one of the quickest and most useful heart tests, taking only a few minutes. It records your heart’s electrical activity and can spot many rhythm problems and signs of heart strain.
Imagine arriving at a clinic with palpitations. A nurse sticks ten small pads on your chest, arms and legs, asks you to lie still, and a printer produces a wavy line. Within minutes, you know your heart rhythm is normal.
What an ECG measures
Every heartbeat is triggered by an electrical signal that spreads through the heart muscle. An electrocardiogram (ECG or EKG) records these signals through sticky electrodes on the skin. The result is a tracing showing the heart’s rate, rhythm and electrical pattern.,A standard ECG is called a 12-lead ECG, because it gives 12 different views of the heart’s electrical activity, even though it uses 10 electrodes.
Why an ECG might be done
- Chest pain or suspected heart attack
- Palpitations, dizziness or fainting
- Breathlessness
- High blood pressure assessment
- Before surgery or starting some medicines
- Monitoring heart conditions or the effects of medicines
- Routine health checks in some situations
What happens during the test
You will usually be asked to undress to the waist; a gown may be provided. Small sticky electrodes are placed on your chest, arms and legs. Some chest hair may need to be shaved for good contact.,You lie still and breathe normally for a short time while the recording is taken. The test is painless, sends no electricity into your body and usually takes about five minutes.
Common terms on an ECG report
- Sinus rhythm: the normal heart rhythm
- Sinus tachycardia: a normal rhythm that is faster than 100 beats per minute, often from exercise, fever, anxiety or dehydration
- Sinus bradycardia: a normal rhythm slower than 60 beats per minute, common in fit people and during sleep
- Atrial fibrillation (AF): an irregular rhythm from the upper chambers
- Ectopic beats: extra beats, usually harmless
- Bundle branch block: a delay in electrical conduction, sometimes harmless and sometimes linked to heart disease
- Left ventricular hypertrophy: signs of thickened heart muscle, often from high blood pressure
- ST changes or T wave changes: patterns that may suggest reduced blood supply, heart strain or other conditions
- Long QT: a prolonged electrical recovery time that can be caused by some medicines or inherited conditions
What an ECG can and cannot show
An ECG is excellent for identifying heart rhythm problems that are happening at the time of the recording, signs of a current or previous heart attack, and some signs of heart strain.,However, a normal ECG does not rule out all heart problems. Narrowed heart arteries may not show at rest, and rhythm problems that come and go may be missed. Your healthcare provider may suggest a heart monitor, echocardiogram or stress test depending on your symptoms.
Getting a good recording
- Avoid body lotion on your chest on the day
- Wear a top that is easy to remove
- Lie still, relax your arms and do not talk during the recording
- Tell the staff if you are cold, as shivering can affect the tracing
- Tell staff about your medicines, as some affect the ECG
Smartwatch ECGs
Some smartwatches can record a single-lead ECG and alert you to possible atrial fibrillation. They can be useful for capturing symptoms when they happen, but they cannot replace a 12-lead ECG, and they can give false alarms. If your device flags a possible problem, or if you have symptoms, see a healthcare provider and bring the recording.
When to seek urgent help
Do not wait for an ECG appointment if you have chest pain, severe breathlessness, fainting or palpitations with feeling very unwell. Call your local emergency number.
Frequently asked questions
Is an ECG painful?
No. Removing the sticky electrodes may tug slightly on hair.
Can women wear a bra?
You will usually need to remove an underwired bra, as electrodes are placed on the chest. A gown or sheet can be used for privacy.
Do I need to prepare?
No special preparation is needed for a resting ECG.
But my ECG was normal and I still have symptoms
Tell your healthcare provider. A single ECG can miss intermittent problems, and other tests may help.
Your next step: If you have palpitations, try to note the time and what you were doing, so an ECG or monitor can be timed well.
Related: Holter monitor · Heart palpitations
Sources: British Heart Foundation, American Heart Association, Society for Cardiological Science and Technology, National Institute for Health and Care Excellence.
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