What it is
An (electrocardiogram, also written EKG) records the tiny electrical signals your heart makes with each beat. The recording shows how fast the heart is beating, whether the rhythm is steady or uneven, and how the signals travel through the heart. The machine only records. It does not send any electricity into your body.
Why it is done
A doctor may ask for an to look for the cause of chest pain, a racing or uneven heartbeat, breathlessness or dizziness. It helps to show whether someone is having a heart attack, or had one in the past. It is also used to follow a heart condition you already have, and sometimes before an operation.
What it helps with
How to prepare
A resting usually needs no special preparation.
Do
- Wear a top that is easy to take off
- Tell the nurse about every medicine you take, as some can change the result
Do not
- Do not put body lotion, oil or talcum powder on your skin
- Do not stop any medicine unless the doctor tells you to
- Do not have a heavy meal or caffeine just before an exercise ECG
What happens
A resting goes like this:
- You take off your top and lie down, usually behind a screen.
- Sticky patches (electrodes) go on your chest, arms and legs, with wires to the machine. Some chest hair may be shaved so they stick.
- You lie still for a few minutes while the machine records. You will not feel anything.
- The patches are peeled off. This can tug a little, like taking off a plaster.
An exercise ECG is done in hospital while you walk on a treadmill or cycle. It stops if you get symptoms or feel too tired. A portable ECG is a small recorder on a belt, worn for 24 to 48 hours, sometimes up to 7 days. You cannot bathe or shower while it is on.
Afterwards
Some people get a slight rash where the patches were. A portable recorder is handed back on the date you were given. You may hear the result on the day, or be asked to come back. If you have heard nothing after a few weeks, contact the doctor who sent you.
Risks and side effects
An carries very little risk. The side effects are mild: some discomfort or skin irritation when the patches come off, and sometimes a slight rash. An exercise ECG makes the heart work harder, so it is done in hospital and stopped if you develop symptoms.
Results and what comes next
A doctor reads the tracing and explains it. A result that is not normal may be a sign of a heart condition, and you may need other tests before a diagnosis is made.
What an cannot show: it is a snapshot of a few minutes, and it records electrical signals, not pictures. A normal resting ECG does not rule out every heart problem. A problem that comes and goes may not happen while you are connected, and the tracing can look normal even in someone with (chest pain from a heart that is short of blood). Doctors read it together with your symptoms and an examination.
An exercise ECG, a stress test, can help show whether narrowed heart arteries are causing chest pain. A portable ECG worn for a day or longer can catch a rhythm problem that comes and goes. An is an scan that shows how well the heart is working, including in heart failure or valve disease.
Questions to ask your doctor
Tick the ones you want answered and take them with you.
Common questions
Does an ECG hurt?
No. The machine only records the heart's signals and sends no electricity into your body. The most you may feel is a little discomfort when the patches are peeled off, and sometimes a mild rash afterwards.
If my ECG is normal, does that mean my heart is healthy?
Not always. A resting ECG shows only a few minutes of the heart's electrical activity, so a problem that comes and goes can be missed, and the tracing can be normal even in someone with angina. If you still have symptoms, tell your doctor, who may suggest a longer recording, an exercise test or a scan.
How long does an ECG take, and when do I get the result?
A resting ECG takes a few minutes. An exercise ECG takes longer, and a portable recorder is worn for a day or two, sometimes up to a week. The result is sometimes ready the same day but can take up to a few weeks depending on the type, so ask when you will hear.
Is an ECG the same as an echocardiogram?
No. An ECG records the heart's electrical signals, while an echocardiogram is an ultrasound scan that shows how well the heart is working. They answer different questions, and a doctor may ask for one, the other or both.
