ECG (Electrocardiogram): what is it and how is it done?

The electrocardiogram is one of the diagnostic examinations most used in assessing heart function. Learn more about how it is done. Click To Tweet

Cardiovascular diseases one of the main causes of death in developed countries and, therefore, it is essential to detect any changes that might compromise heart function in good time. Here, the electrocardiogram (or ECG) plays an important role in diagnosing heart pathology. We will address the main questions concerning this examination.

What is an electrocardiogram (ECG)?

The electrocardiogram is a non-invasive diagnostic examination that detects the heart’s electrical activity.  Every contraction of the heart muscle or heart valves emits an electric pulse that can – or not – be considered normal. The ECG manages to identify whether there are changes, focusing the diagnosis and therapeutic requirements. 

When is performing an electrocardiogram (ECG) recommended?

The electrocardiogram is the examination most recommended for detecting heart arrhythmias or indications of cardiac ischemia. It is furthermore important in assessing other heart changes, namely:

  • Heart-valve illnesses
  • Cardiomyopathy
  • Pericarditis
  • Heart side effects of arterial hypertension

In the case of patients with complaints of chest pain, fatigue, difficulty breathing, dizziness or other symptoms that might suggest heart disease, it is the first examination to be performed.

How is the electrocardiogram (ECG) performed?

The electrocardiogram is conducted by a cardiopulmonology technician. Once the outline has been obtained (which will be printed out), it is then examined by the Cardiologist. The following procedures are conducted in performing the electrocardiogram at rest:

  • Confirming the identity and recording the personal details of the patient (full name and date of birth), following by the clinical history important for correctly interpreting the examination.
  • The patient then lies down unclothed, in a peaceful environment and without any stimuli in order to obtain the correct outline.
  • Six electrodes are placed on the chest, one on each of the lower limbs, which will be linked by wires to the electrocardiograph. A gel to increase electrical conductivity may be applied topically.
  • Following this link and once the data is collected, an outline will be printed out on thermal graph paper, which will subsequently be interpreted by the cardiologist.
ECG (Electrocardiogram): what is it and how is it done?

What are the different types of electrocardiogram (ECG)? 

The ECG performed at rest is the one most used. However, there are other types of electrocardiogram that can be performed, namely:

  • Exercise ECG: the electrodes of the ECG at rest are used and, in addition, a treadmill or exercise bike are also required. This examination makes it possible to assess the heart under stress conditions and to identify illnesses such as angina.
  • Holter ECG: this examination records heart activity over 24 hours. This way, the heart’s activity during this time can be studied, taking the different activities and possible symptoms of illnesses into account.

There are no risks associated with performing the ECG. Only a slight allergy to the adhesives placed on the chest is possible, in certain cases. In the event of patients with a lot of hair in the chest area, it might also be necessary to remove this in order to improve the adhesion of the electrodes to the skin.

How to prepare for an ECG: Is prior preparation required? What precautions should be taken?

No preparation is required. However, it is advisable for the patient not to exert themselves in the 10 minutes prior to the examination, nor to consume any stimulant drinks, such as coffee. Neither is it advised to smoke 30 minutes before the examination is performed.


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