During electrocardiography (ECG), electrical signals from each heartbeat are transmitted from electrodes on the patient's skin to a machine that creates a graph of the rhythm and rate of the heartbeat.

ECG helps physicians evaluate the following:

• Arrhythmias;
• Chest pain;
• Myocardial infarction;
• Structural heart problems;
• Metabolic or hemodynamic changes;
• A person's response to therapy;
• Pacemaker monitoring; and
• A person's heart before surgery.

There are 3 forms of ECG testing:

• Resting ECG;
• ECG stress test; and
• Ambulatory ECG.

PRE-TEST GUIDELINES

Patients should not exercise strenuously just before the test.

WHAT TO EXPECT

The patient lies down and approximately 10 electrodes are attached to the person's chest and back. The electrodes record the heart's electrical impulses and transmit them to an electrocardiograph. The electrodes may be placed on top of a light layer of gel that conducts electricity.

The procedure differs for the variations of ECG:

• ECG stress test. The patient walks on a treadmill or the heart is simulated with drugs.
• Ambulatory ECG. The patient's heart is monitored away from the physician's office.

POST-TEST GUIDELINES

Most patients can resume normal activities following an ECG test.