Electrocardiography (ECG)

The electrocardiogramA tracing of the electrical activity of the heart., usually abbreviated to ECGAbbreviation for electrocardiogram, a tracing of the electrical activity of the heart to help in the diagnosis of heart disease. or EKG, is very helpful in assessing whether a person is having, or has had, a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction.. However, an ECGAbbreviation for electrocardiogram, a tracing of the electrical activity of the heart to help in the diagnosis of heart disease. does not always show changes even when a person is having a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. - sometimes it is entirely normal.[1] In fact, the ECGAbbreviation for electrocardiogram, a tracing of the electrical activity of the heart to help in the diagnosis of heart disease. is normal in a fifth of heart attacks in the early stages.[2]

When changes are seen, the ECGAbbreviation for electrocardiogram, a tracing of the electrical activity of the heart to help in the diagnosis of heart disease. may show whether the heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. affects the full thickness of the heart muscleTissue made up of cells that can contract to bring about movement. wall, or whether just part of the wall is affected.[1]

An ECGAbbreviation for electrocardiogram, a tracing of the electrical activity of the heart to help in the diagnosis of heart disease. is quick and easy for the doctor to do and a reading is given almost immediately, which means the findings of the test can be used to guide emergency treatment.

Although an ECGAbbreviation for electrocardiogram, a tracing of the electrical activity of the heart to help in the diagnosis of heart disease. is not as sensitive at detecting a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. as some bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. tests (these bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. tests look for biochemical markers of heart muscleTissue made up of cells that can contract to bring about movement. damage; see below), the ECGAbbreviation for electrocardiogram, a tracing of the electrical activity of the heart to help in the diagnosis of heart disease. is much quicker - whereas it usually takes several hours for the levels of biochemical markersCertain substances found in the blood or other body fluid that indicate a disease when detected. to increase.[3]

ECGs are very sensitive at picking up heart attacks, meaning that although an  ECGAbbreviation for electrocardiogram, a tracing of the electrical activity of the heart to help in the diagnosis of heart disease. may be normal during an attack, most people having a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. will show ECGAbbreviation for electrocardiogram, a tracing of the electrical activity of the heart to help in the diagnosis of heart disease. changes .[3] ECGs are also very specific for heart attacks.[4] This means that if an ECGAbbreviation for electrocardiogram, a tracing of the electrical activity of the heart to help in the diagnosis of heart disease. suggests a person is having a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction., he or she almost certainly is having one.

Once the emergency is over, if someone has had a heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. or is suspected to be at high risk for one, another type of test may be performed that involves recording  an ECGAbbreviation for electrocardiogram, a tracing of the electrical activity of the heart to help in the diagnosis of heart disease. while the person is running on a treadmill. This is called an exercise ECGAbbreviation for electrocardiogram, a tracing of the electrical activity of the heart to help in the diagnosis of heart disease. or stressRelating to injury or concern. test.

The reasoning behind doing this is that exercise puts the heart under extra stressRelating to injury or concern. - bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. flow through the heart can actually quadruple in response to exercise. Because of this, changes are sometimes seen during an exercise ECGAbbreviation for electrocardiogram, a tracing of the electrical activity of the heart to help in the diagnosis of heart disease. that were not there when an ECGAbbreviation for electrocardiogram, a tracing of the electrical activity of the heart to help in the diagnosis of heart disease. was taken with the person simply at rest.[5]

Learn more about ECGs.

References: 
  1. Boon NA, Colledge NR and Walker BR. Davidson's Principles and Practice of Medicine. Churchill Livingstone Elsevier. 2006; 20th edition.
  2. Longmore M, Wilkinson I, Török E. Oxford Handbook of Clinical Medicine. 2002; 5th edition.
  3. ECGAbbreviation for electrocardiogram, a tracing of the electrical activity of the heart to help in the diagnosis of heart disease. diagnosisThe process of determining which condition a patient may have. of acuteHas a sudden onset. ischaemiaInsufficient oxygenation to a part of the body due to poor blood supply. and infarction: past, present and future. Herring N and Paterson DJ. Q J Med 2006;99:219-30.
  4. Improving the early diagnosisThe process of determining which condition a patient may have. of acuteHas a sudden onset. myocardial infarctionDeath of an area of heart muscle due to poor blood supply.. Banerjee A. Postgrad Med J 1996;72:705-8.
  5. Myocardial perfusion imaging: a validated and mature cardiac imaging modality. Australian Family Physician 2006;35:288-92.