The ECG test and your heart

Powering the heart...

Given the prevalence of heart disease in Ireland it is quite likely that most Irish adults will undergo an ECG examination at some stage in their adult lives. Therefore, it might be useful and interesting to know something about the test. In the year 2000, just over one fifth of all deaths in Ireland were due to ischaemic heart disease. This amounted to a death toll of 6,600 people, of which 4,100 were due to heart attack.

Many thousands of Irish people suffer from various conditions of the cardiovascular system including angina, high blood pressure and heart failure. The acronym ECG stands for electrocardiogram and is sometimes alternatively referred to as an EKG or cardiogram. It was invented in 1903 by a Dutch physiologist by the name of Willem Einthoven. His pioneering work resulted in him being awarded the Nobel Prize in 1924.

Electrical activity

Today there are tens of thousands of electrocardiograms in use throughout the world. Although modern equipment may look a little different to the devices developed by Einthoven the basic principles remain the same. The electrocardiogram detects and records the pattern of electrical activity in the heart and the pattern is recorded on special graph paper. This paper record is known as an electrocardiograph.

The heart has its own power source but if it fails, a pacemaker may be inserted.

Many people will have heard of artificial pacemakers but may not be aware that the heart has its own inbuilt pacemaker, which we refer to as the sino-atrial or SA node. This tiny structure emits an electrical impulse, which is conducted through the electrical conducting system of the heart. This electrical impulse stimulates the cardiac muscle to contract resulting in pumping of the blood through the chambers of the heart and out though the general circulation. The ECG detects and records this electrical activity and the tracing allows the doctor to reach certain conclusions regarding cardiac function.

ECGs are performed for a variety of reasons. A doctor may recommend an ECG in order to evaluate various symptoms such as chest pain or an irregular heart beat. Alternatively the test may be used to evaluate the state of heart health in people with various risk factors such as high blood pressure and raised cholesterol levels. Sometimes it may be performed on people with no symptoms of the disease that happen to have a family history of heart disease. In some cases they may even be used as a form of reassurance in people who are anxious about the possibility of having heart disease.


The ECG is also useful for long term follow up of a person with known heart disease. One record can be compared with the next and indicate if significant change in cardiac function has happened in the interim. People with artificial pacemakers are well used to having regular ECGs in order to establish that their artificial pacemaker is discharging effectively. Artificial pacemakers are fitted in situations where the SA node is faulty and not discharging properly.

The treadmill fitness test.

The test can be performed in the surgery or at the hospital. It is important to realise that the test is painless and does not discharge any electricity into the person being examined. Rather it is measuring the low voltage electricity that is being discharged within the heart itself. It is customary for the person to strip to the waist for the examination. The person usually lies down for the test and a series of electrodes is applied to the wrists, ankles and chest. The electrodes act as sensors and a special jelly is applied to the skin, which helps to improve electrical conduction through the electrodes. The test takes less than ten minutes to perform.

There are a number of variations on the basic ECG and these include Holter monitoring and stress testing. The Holter monitor can be thought of as a continuous ECG that is recorded over an extended period of time. The recording is usually made over a 24-hour period. A small walkman-like device is worn on the waistband of the trousers and is connected with thin wires to a series of electrodes that are attached to the chest wall. The electrodes are disposable and have a rim of adhesive, which enables them to stick to the chest wall throughout the day of the test. It is not possible to shower or bathe when undergoing Holter monitoring.

Fainting and dizziness

Holter monitoring is frequently used for the elucidation of symptoms such as faintness and dizziness that may be cardiac in origin. Sometimes these symptoms may be due to abnormalities of rhythm that may not be detectable with the more traditional form of ECG. Rhythm disturbances tend to be intermittent and it may simply happen that the abnormality is not present when the traditional ECG is being performed. Holter monitoring gets over this common difficulty.

The person undergoing Holter monitoring is advised to wear a wristwatch and also to document on paper the timing and nature of any symptoms they develop during the course of the test. People may sometimes be aware of irregularity in the beating of the heart so it is possible to marry the recording on the monitor with the person’s contemporaneous written account of what they actually experienced.

The cardiac stress test is another form of ECG and as the name suggests the recording is made while the heart is being stressed through physical exercise. This test is always performed under medical supervision because unlike the two previously described tests it is not without risk. Some people may develop significant chest pain or other cardiac symptoms during the test. Throughout the test the person’s blood pressure is measured frequently and the monitor is closely observed for any ECG changes. If such changes do develop the doctor aborts the test.

Stress test

The person walks on a treadmill throughout the test. People are usually advised to wear light loose clothing and comfortable walking shoes when undergoing a stress test. It is also important not to smoke or drink too much teat or coffee in the hours preceding the test because these may cause ECG changes and skew the test result. The treadmill starts slowly at a slight incline and gradually the speed and incline increases. Electrodes are attached to the patient’s chest just as with the Holter monitor and the ECG is observed throughout the test. The test is stopped when the person gets tired and can’t walk anymore on the treadmill.

Depending on the state of cardiac function the person may have to stop after a couple of minutes or may be able to keep on going for twenty. Although the test gives useful information it gives no indication of the possible degree of blockage in the coronary arteries. That specific information requires further investigation with a coronary angiogram.

The ECG is a very useful diagnostic tool that is painless and patient friendly. It is quite likely that you will undergo this test some day, in which case you have absolutely nothing to fear from the test itself.

Dr Leonard Condren is the medical editor of


Mark(ryanmk) - 20/02/2002 08:25

I'm 32 and reasonably fit. I've had a few ECG's over the last number of years because of my times in hospital for wisdom teeth removal, removal of splinter from finger (surgery) etc. My first ECG was about 10 years ago when a regular medical with my GP suggested I might have a heart murmur. On return he could not hear the murmur and concluded it was a 'flowing murmur'. I've had a chest x-ray and ultrasound scan done also. All seemed to be positive. Recently my Dad died of suspected heart failure (post mortem results not yet released). Since then and I've felt irregularities in my heart. Could these be brought on by stress/anxiety caused by my recent loss? Are there any other symptoms I should look for for suspected heart related problems. Reports from blood pressure tests done over the years suggest that I have slightly high blood pressure but the medical staff suggested that that may be down to the stress caused by the test. I don't feel I suffer from stress too much. Any comments would be appreciated. Thanks

Anonymous - 20/02/2002 16:20

I'm 64 (female) In 1985 I began to have an irregular heart beat, it was then discovered that I had a defective mitral valve & was prescribed Sotacor 40mg twice daily. Recently I notice I have the irregularities again (at rest) but the beats seem very weak. Should I request an ECG again? Please give me more information if possible.Many thanks.I enjoy reading your website each week.

Dara(Dara_Hogan) - 20/02/2002 18:30

I did OK on my stress ECG but the doc told me they were glad to see me wearing my old, well-worn squash shoes. They get worried about the guys who arrive sweating, stinking of tobacco smoke and carrying a LifeStyle bag containing brand new trainers! >>> Dara <<<

carol(nirvana) - 21/02/2002 00:30

i read this article because I recently had one done for the first time. It had been noticed that my pulse was very low even after aerobic exercise and I decided to have a health screening which included an ecg. The article was very straightforward and easy to understand...Thank you.

Garry(Garrry) - 21/02/2002 01:57

Ive read the article and will be getting a holter test soon....... I now know more and dont feel so bad

miriam(miriammatthews) - 22/02/2002 10:32


Elton J Twomey(Elton) - 27/02/2002 00:06

I read the article and because of family history, I think I'll think will inquire into getting an ecg done.

Ruth(ruthking) - 23/05/2002 21:38

I am going for a Holter test next week after discovering through a stress test that I have an irregular heart beat when under exertion or anxiety or stress. Can you please give me more information? I find your site very helpful and very informative.

Anonymous - 18/06/2002 12:15

Im 26 and in last few weeks im getting little twinges in my heart but it seems to be beating normally. Does anyone know what this is?????

Ruth(ruthking) - 18/06/2002 20:32

Don't get alarmed if you are told your heart has stopped for 968secs. over 24 hrs.! I had a Holter test done and had to have it repeated and got similar results again the second time. The doctor has now informed me that the monitor was possibly faulty! So much for avoiding stress. I will now have to have it repeated for the third time. Believe me, I am not too impressed.

Anonymous - 26/06/2002 23:50

I had a stress test done and I have now to go for an angiogram Please tell me what this is and is it dangerous. Will it show up what is wrong with my heart Please give me an answer as soon as possible as I am worried.

Anonymous - 03/07/2002 12:17


Bernie(Estartit) - 31/07/2002 14:38

I had a Stress/ECG test in early June due to a tightness in my chest and a history of heart disease in my family. I am reasonably fit and I got positive results. I would definitely recommend it for anyone who is concerned about the state of their heart.

denis(denism) - 02/08/2002 01:11

I get occassional pains in my chest but when I had a ECG done it was found there was no problem but at the same time I would like to know what causes same,any suggestions.I am aged 46.

Garry(Garrry) - 02/08/2002 23:27

Hi all, I have been put on some medication for high blood presure and am trying to get my weight down. My doc is not happy with my blood presure... but i am getting better a bit i hope. thanks

Anonymous - 10/09/2002 14:36

My Mother had a heart bypass 10 years ago and my father had 2 treble bypasses, he recently died of heart failure. All my aunts and uncles on both sides of my family with the exception of one has had heart bypasses of died of heart problems. I'm 26 should I have a ecg and what is the likelyhood of developing heart problems with my family history.

Derek(Derek-MP) - 10/10/2004 07:25

What is "right bundle branch block"?

Anonymous - 13/04/2005 22:47

i recently had a ecg i am 25 it came back normal the problem is i wasnt getting skipped beats when i was on it so im still at my worrying stage. i am now being put on a 24hr monitor i hope all goes well could you tell me what this test will show plz.

Anonymous - 23/04/2005 12:21

Anonymous 13/04/05. 24 hour monitor will just show up any palpitations or skipped beats etc. I had this done twice once when I was 14 and again when I was 19. The first time I'm not sure if it showed anything but it turned out I had SVT. The test is fine and just helps them to pin point the problem. hope this helps!

nichola(JXA26580) - 24/04/2005 14:06

what is svt can your heart be normal even if you get the skipping of the beat. can it just be stress related cause i get panic attacks also.

Anonymous - 12/05/2005 19:07

I had a stress test that consisted of 10 minutes very slow walking on a treadmill. At no time was I out of breath and continued chatting to the nurse. I asked was it meant to be a bit more energetic and was told that if I could increase my heart rate by 20% without any pain or anything showing up on the ecg, then there was no problem. I am not reassured and feel this was a rip off as I had to pay 250 euro for this as there is a 2 year wait to have it done in the public out-patients.

Anonymous - 21/07/2005 11:26

Recently I passed out failed to come around and was brought to hospital by ambulance. There they found an irregular heart beat, I was kept in overnight for observation and released the following morning with a letter for my GP to refer me to my local hospital for a Holter test. My local doctor said I was fine there was no history of heart problems in our family and to take it easy he did not refer me for the test. I don't suffer from stress but do get dizzy often. I do have low blood pressure. Should I ask again for this test?

Anonymous - 21/07/2005 15:46

To Anon posted 21/07/05 If there is anything I have learned from doctors you have to tell them to refer you. If the hospital thinks you need a holter done then you should get your doctor to refer you. A holter monitor records your heart for 24 hours. you go to hospital and hook it up and then you come back in 24 hours. If you are worried also make sure your doctor does something or else see another doctor. hope this helps.

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