Electrocardiography (ECG)

What is an Electrocardiography or ECG?

Electrocardiography (ECG) is a trans-thoracic (across the thorax or chest) interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the surface of the skin and recorded by a monitoring device external to the body.The recording produced by this noninvasive procedure is termed an electrocardiogram (also ECG).

An ECG(also 12 lead ECG) is used to measure the rate and regularity of heartbeats, as well as the size and position of the chambers, the presence of any damage to the heart, and the effects of drugs or devices used to regulate the heart, such as a pacemaker.

 normal ECG with normal Sinus Rhythm

Why is an Electrocardiography or ECG done?

An ECG is the best way to measure and diagnose abnormal rhythms of the heart, particularly abnormal rhythms caused by damage to the conductive tissue that carries electrical signals, or abnormal rhythms caused by electrolyte(mainly Potassium and Magnesium) imbalances. In a Heart Attack(Acute Myocardial Infarction) the ECG can identify if the heart muscle has been damaged in specific areas, though not all areas of the heart are covered.The ECG cannot reliably measure the pumping ability of the heart, for which ultrasound-based (Echoecardiography) or nuclear medicine tests are used. It is possible for a Patient to be in Cardiac Arrest, but still have a normal ECG signal (a condition known as pulseless electrical activity).

A normal, regular and healthy rhythm is called Sinus Rhythm(SR)

Other abnormal or irregular heart rhythms are

  • Atrial Fibrillation(AF)
  • Atrial Flutter
  • Supraventricular tachycardia (SVT)
  • Ventricular Tachycardia(VT)
  • Ventricular Fibrillation(VF)


The ECG device detects and amplifies the tiny electrical changes on the skin that are caused when the heart muscle depolarizes(relaxes) during each heartbeat.

Usually, an ECG can be performed whilst your loved one is attached to the Bedside Monitors, however some extra electrodes may have to be attached to your loved ones chest whilst performing the (12-lead) ECG. This is a risk free and quick procedure and is usually performed once daily while your loved one is in Intensive Care. If your loved one has irregularities in his or her heart rhythm, he or she will need ECG’s done quite regularly, to assess effectiveness of treatment for the heart.

Any Questions?

Of course, if you have any questions or concerns, please discuss them with the ICU nurses and doctors.

All Intensive Care interventions and procedures carry a degree of potential risk even when performed by skilled and experienced staff. Please discuss these issues with the medical and nursing staff who are caring for your loved one.

The information contained on this page is general in nature and therefore cannot reflect individual Patient variation. It is meant as a back up to specific information which will be discussed with you by the Doctors and Nurses caring for your loved one. INTENSIVE CARE HOTLINE attests to the accuracy of the information contained here BUT takes no responsibility for how it may apply to an individual Patient. Please refer to the full disclaimer.

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