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Heart Institute at Children’s Hospital of Pittsburgh of UPMC

Electrocardiogram (EKG/ECG)
An electrocardiogram (EKG or ECG) is one of the simplest and fastest procedures used to evaluate the heart. Small plastic patches called electrodes will be placed at certain spots on your child's chest, arms, and legs. When the electrodes are connected to the EKG machine by lead wires, the electrical activity of your child's heart is measured, interpreted, and printed out for the doctor's information and further interpretation. Changes in an EKG from the normal tracing can indicate one or more heart-related conditions.

Many medical conditions can cause changes in the EKG pattern, such as:

  • heart enlargement, which can be caused by factors such as congenital (present at birth) heart defects, valve disorders, high blood pressure, congestive heart failure, or conduction disturbances
  • ischemia, a decreased blood flow to the heart muscle, due to clogged or partially-clogged arteries
  • conduction disorders, a dysfunction in the heart's electrical conduction system, which can make the heart beat too fast, too slow, or at an uneven rate
  • electrolyte disturbances, an imbalances in the level of electrolytes, or chemicals, in the blood, such as potassium, magnesium, or calcium
  • pericarditis, an inflammation or infection of the sac that surrounds the heart
  • valve disease, a malfunction of one or more of the heart valves which may cause an obstruction of the blood flow within the heart
  • chest trauma, a blunt trauma to the chest

An EKG also may be performed for many other reasons, including to:

  • get a baseline tracing of the heart's function that can later be used as a comparison with future EKGs to track changes
  • make sure no heart condition exists that might cause complications as part of a work-up prior to a procedure or surgery
  • check the function of an implanted pacemaker
  • measure the effectiveness of certain heart medications
  • confirm the heart's status after a heart-related procedure such as a cardiac catheterization, heart surgery, or electrophysiological studies

What an EKG Tracing Shows
An EKG tracing consists of several spikes and valleys, each of which measures a different part of your child’s heartbeat.

  • The first little upward notch of the EKG tracing is called the P wave. The P wave indicates that the atria (the two upper chambers of the heart) are electrically stimulated to pump blood to the ventricles.
  • The next part of the tracing, a short downward section connected to a tall upward section, is called the QRS complex. It indicates that the ventricles (the two lower chambers of the heart) are electrically stimulated to pump out blood.
  • The next short flat segment is called the ST segment. The ST segment indicates the amount of time from the end of the contraction of the ventricles to the beginning of the T wave.
  • The next upward curve is the T wave. The T wave indicates the recovery period of the ventricles.

When your child's doctor studies your child's EKG, he or she looks at the size and length of each part of the EKG. Variations in size and length of the different parts of the tracing may be significant. The tracing for each lead of a 12-lead EKG will look different, but will have the same basic components as described above. Each lead of the 12-lead is "looking" at a specific part of the heart, so variations in a lead may indicate a problem with the part of the heart associated with that lead.

Depending on the results of the EKG, additional tests or procedures may be scheduled to gather further diagnostic information.

View the patient procedure sheet about eclectrocardiogram at Children’s Hospital.

Last Update
August 21, 2012
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Last Update
August 21, 2012