Electrocardiography (ECG)

         Basic Facts

  • The electrocardiogram (ECG) is a diagnostic test to record the electrical activity of the heart. An ECG detects the tiny electrical impulses produced by the heart to make it contract. 
  • An ECG is commonly used to establish a baseline evaluation of a person’s heart, to detect abnormal heart rhythms, and to investigate newly evolving symptoms, such as chest pain, shortness of breath, or palpitations.
  • Physicians use different forms of ECG testing, including resting, stress, and ambulatory ECG.
  • A resting ECG may be done first because it may show a heart problem that would make an ECG stress test unsafe.

During electrocardiography (ECG), electrical signals from each heartbeat are transmitted from electrodes on the patient’s skin to a machine that creates a graph of the rhythm and rate of the heartbeat.

ECG helps physicians evaluate the following:

  • Locate areas of the heart that receive an insufficient blood and oxygen supply,
  • Reveal heart rhythm abnormalities,
  • Evaluate a person’s prognosis after a heart attack, and
  • Verify the effectiveness of medical and surgical therapies.
There are three forms of ECG testing: 
  • Resting ECG – This test is usually performed while a patient lies on a table,
  • ECG stress test – The stress test monitors a heartbeat during exercise, most commonly while a person walks on a treatmill.
  • Ambulatory ECG  - This test records the electrical activity of the heart while a patient does usual activities. For example, the patient may wear a Holter monitor, a battery-operated portable device that measures heart activity continuously for 24 hours, or several days, or even weeks.  

Electrocardiography (ECG) FAQ