Electrocardiogram (ECG/EKG)

What is an electrocardiogram (ECG)?

An electrocardiogram (ECG or EKG) is a simple and fast procedure used to evaluate the heart. Electrodes (small stickers) are placed on your child's chest, arms, and legs. When the electrodes are connected to the ECG machine by wires, the electrical activity of your child's heart is measured, interpreted, and printed out for the doctor's further interpretation.

Why is an ECG done?

An ECG measures the electrical activity of the heart. By placing electrodes at specific locations on the body (chest, arms, and legs), a tracing of the heart's electrical activity is made. Changes in an ECG from the normal tracing can mean one, or more, of several heart-related conditions.

Some medical conditions which may cause changes in the ECG pattern include:

  • Conditions in which the heart is enlarged. These conditions can be caused by various factors, such as congenital heart defects, valve disorders, high blood pressure, or heart failure.

  • 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 imbalance in the level of electrolytes, or chemicals, in the blood, such as potassium, magnesium, or calcium.

  • Pericarditis. An inflammation or infection of the sac which surrounds the heart.

  • Valve disease. Malfunction of one or more of the heart valves that may interfere with blood flow within the heart.

  • Chest injury. Injury to the chest, such as from an automobile accident.

This list is an example. It is not a complete list of all conditions which may cause changes in the ECG pattern.

An ECG may also be done for other reasons, including:

  • During a physical exam to obtain a baseline tracing of the heart's function (This baseline tracing may be used later as a comparison with future ECGs, to see if any changes have occurred.)

  • As part of a workup prior to a procedure, such as surgery, to make sure no heart condition exists that might cause complications during or after the procedure

  • To check the function of an implanted pacemaker

  • To check the effectiveness of certain heart medications

  • To check the heart's status after a heart-related procedure, such as a cardiac catheterization, heart surgery, or electrophysiological studies

What does an ECG means?

Almost everyone knows what a basic ECG tracing looks like. But what does it mean?

Illustration of a basic EKG tracing

  • The first little upward notch of the ECG 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 short, flat segment is called the "PR interval." This represents the delay in the propagation of the electrical signal from the atria to the ventricles.

  • The next part of the tracing is a short downward section connected to a tall upward section. This next part is called the "QRS complex." This part 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 after contraction.

When the doctor studies your child's ECG, he or she looks at the size and length of each part of the ECG. Variations in size and length of the different parts of the tracing may be significant. The tracing for each lead of a 12-lead ECG 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 the lead.

What is the procedure for an ECG?

An ECG can be done almost anywhere, as the equipment is very compact and portable. Your child may have an ECG in a doctor's office, a clinic, in the emergency department, or even in the hospital room or bed. The equipment used includes the ECG machine, skin electrodes, and lead wires which attach the electrodes to the ECG machine.

An ECG normally takes about  5 to 10 minutes, including attaching and detaching electrodes.

An ECG typically includes the following steps:

  • Your child will lie flat on a table or bed for the procedure.

  • The ECG technician will need to have your child's chest uncovered in order to do the test. Your child will be covered with a sheet or gown and exposing only the necessary skin.

  • Electrodes (small, plastic patches) will be attached to your child's chest and one electrode will be attached to each arm and leg.

  • The lead wires will be attached to the skin electrodes.

  • Once the leads are attached, the technician may key in identifying information such as your child's name and age into the machine's computer.

  • The ECG is started. It will be important for your child to lie still and not talk during the procedure, so as not to interfere with the tracing. Parents can usually be present in the room and involved in reassuring and encouraging their child during the procedure. At this point, it will take only a few minutes (or less) for the tracing to be completed.

  • Once the tracing is done, the technician will disconnect the leads and remove the skin electrodes.

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