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Basic Explanation

This test, also known as an ECG or EKG, records the movement of electrical charges across the heart using a machine known as an electrocardiograph.  The changes in electrical activity over time are recorded on a piece of paper. This produces an undulating line, or tracing, which may be used to diagnose various heart defects or abnormalities.

In order to produce an ECG, a number of electrodes (usually 12) are placed on the skin of the patient's chest and limbs with adhesive patches. Numerous electrodes are necessary in order to give a complete view of the heart’s activity.  The skin will be cleansed and possibly shaved at the points of electrode attachment to insure a high level of contact.

The patient should avoid vigorous exercise or drinking cold drinks before the procedure. While the ECG is being taken, the patient will need to avoid moving as this may affect the results.  The patient may be asked to hold his or her breath briefly during the testing procedure. 

An electrocardiogram does not hurt, although young children may find the process scary.  No electricity is transmitted through the body.  The cardiologist will evaluate the electrocardiogram at the time of the patient's visit.

What if abnormal rhythms are present?

Abnormalities of heart rhythm include bradycardias, in which the heart is beating too slow, and tachycardias, in which the heart is beating too fast.  There are also abnormalities in which the heart rhythm is irregular or the different parts of the heart are abnormally involved in rhythmic contraction. 
Abnormalities of the heart's rhythm are treated in various ways. Medications may be used alone or in conjunction with other procedures or devices (such as pacemakers) to restore normal cardiac activity.