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Maine Heart Center - EKG

An electrocardiograph (ECG or EKG) is a graphical representation of the electrical currents produced by the heart while it beats. In a 12-lead ECG the patient, who is sitting or lying down, has twelve stick-on electrodes attached to the skin to detect these electrical impulses. In turn, these leads are connected by wires to a printer which records the heart's pattern of electrical activity.

A normal heartbeat produces a specific pattern of waves. Different kinds of cardiac damage and disease result in other configurations. Hence, an ECG is a diagnostic tool that can pinpoint the location and extent of an injury to the heart. It can also show how the heart is responding to treatment.

A stress ECG is taken while a patient is exercising on a treadmill or bicycle. This shows whether the heart is receiving an ample supply of oxygen as the demand on the heart increases. If the quantity of oxygen decreases while the demand increases, the ECG will change in predictable ways. If someone is unable to exercise, then a drug may be administered to simulate such activity. Some of the most common reasons why such tests are done include the following:

  • To see if an asymptomatic person has silent coronary artery disease, such as blockages or hardening of the arteries of the heart. Here the cardiologist hopes to detect a problem before the usual symptom of a heart attack or even death.
  • To determine if a person's symptoms (such as chest discomfort or difficulty breathing) are due to heart disease rather than another problem.
  • To see if the treatment being given to a patient for blocked arteries is working properly.
  • To assess a person's exercise tolerance before beginning an exercise or cardiac-rehabilitation program. To determine if exercise causes an abnormal heart rhythm.

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