Electrocardiogram
(ECG or EKG)

Medical Author: Daniel Lee Kulick, M.D.
Medical Editor: William C. Shiel, Jr., MD, FACP, FACR

• What is an electrocardiogram (ECG, EKG)?
• How is an ECG (EKG) performed?
• What is measured or can be detected on the ECG (EKG)?
• When is an ECG (EKG) performed?
• What conditions may be diagnosed with an ECG (EKG)?
• What are the limitations of the ECG EKG)?

What is an electrocardiogram (ECG, EKG)?

The electrocardiogram (ECG or EKG) is a noninvasive test that is used to reflect underlying heart conditions by measuring the electrical activity of the heart. By positioning leads (electrical sensing devices) on the body in standardized locations, information about many heart conditions can be learned by looking for characteristic patterns on the ECG.

How is an ECG performed?

ECG leads are attached to the body while the patient lies flat on a bed or table. Leads are attached to each extremity (4 total) and to 6 pre-defined positions on the front of the chest. A small amount of gel is applied to the skin, which allows the electrical impulses of the heart to be more easily transmitted to the ECG leads. The leads are attached by small suction cups, Velcro straps, or by small adhesive patches attached loosely to the skin. The test takes about 5 minutes and is painless. In some instances, men may require the shaving of a small amount of chest hair to obtain optimal contact between the leads and the skin.

What is measured or can be detected on the ECG?

1. The underlying rate and rhythm mechanism of the heart.
2. The orientation of the heart (how it is placed) in the chest cavity.
3. Evidence of increased thickness (hypertrophy) of the heart muscle.
4. Evidence of damage to the various parts of the heart muscle.
5. Evidence of acutely impaired blood flow to the heart muscle.
6. Patterns of abnormal electric activity that may predispose the patient to abnormal cardiac rhythm disturbances.

When is an ECG performed?

1. As part of a routine physical examination or screening evaluation.
2. As part of a cardiac exercise stress test.
3. As part of the evaluation of symptoms of chest pain, shortness of breath, dizziness or fainting, or palpitations.

Next: What conditions may be diagnosed with an ECG (EKG)? »

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