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An electrocardiogram (ECG) is one of the simplest and fastest tests used to evaluate the heart. Electrodes (small, plastic patches that stick to the skin) are placed at certain locations on the chest, arms and legs. When the electrodes are connected to an ECG machine by wires, the electrical activity of the heart is measured, interpreted and printed out. No electricity is sent into the body and there is nothing painful or uncomfortable involved in an ECG.

Here's how it works: Natural electrical impulses coordinate contractions of the different parts of the heart to keep blood flowing in the right directions, and in the proper amounts. An ECG records these impulses to show how fast the heart is beating, the rhythm of the heartbeats and the strength and timing of the electrical impulses. Changes in an ECG can be a sign of many heart-related conditions.

Reasons to Take an Electrocardiogram

There are many reasons your doctor or cardiologist may order an ECG, included as part of a thorough physical or certain life insurance exams. Some specific reasons include:
  • To look for the cause of chest pain (angina)
  • To evaluate problems which may be heart-related, such as severe tiredness, shortness of breath, dizziness or fainting
  • To identify irregular heartbeats (arrhythmias)
  • To help determine the overall health of the heart prior to procedures such as surgery
  • To see how an implanted pacemaker is working
  • To determine how well certain heart medications are working
  • To get a baseline reading of the heart's function during a physical exam (to be used as a comparison with future ECGs)

Electrocardiograms are Very Low-Risk

An electrocardiogram (ECG) is a quick, easy way to assess the heart's function. Risks associated with ECG are minimal and rare. There are certain factors or conditions, however, which may interfere with or affect the results of the ECG. These include:
  • Obesity
  • Pregnancy
  • Ascites (fluid buildup in the abdomen)
  • Anatomical considerations, such as the size of the chest and the location of the heart within the chest
  • Movement during the procedure
  • Exercise or smoking prior to the procedure
  • Certain medications
  • Electrolyte imbalances, such as too much or too little potassium, magnesium, and/or calcium in the blood

What Happens During an Electrocardiogram?

An electrocardiogram may be done on an outpatient basis or as part of your hospital stay. In a private examination room, the technician will ask you to lie on a bed or table. Certain areas of your arms, legs and chest will be cleaned and, in some instances, shaved. This provides a clean, smooth surface for attaching the electrodes.

Several electrodes are attached to the skin on each arm and leg and on your chest, sometimes along with a dab of electrode paste to aid in electrical conductivity. The electrodes, then, are hooked to the ECG machine. During the test, you will be asked to lie very still and breathe normally. Sometimes you may be asked to hold your breath. You should not talk during the test.

Once the test is completed – usually after only 5 or 10 minutes – the electrodes are carefully removed, and any electrode paste is wiped off. Understanding Electrocardiogram Results

Your ECG will be read and interpreted by a doctor, like one of the cardiologists at Baylor Scott & White Heart and Vascular Hospital – Dallas. The doctor will look at the pattern of spikes and dips on your ECG to check the electrical activity in different parts of your heart as your heart goes through its beating cycle. The spikes and dips are grouped into different sections that show your doctor how your heart is working.

  • The heart beats in a regular rhythm, usually between 60 and 100 beats per minute.
  • The ECG tracing looks normal.
  • The heart beats too slow (such as less than 60 beats per minute).
  • The heart beats too fast (such as more than 100 beats per minute).
  • The heart rhythm is not regular.
  • The ECG tracing does not look normal.

More Information

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