An electrocardiogram (ECG) is one of the simplest and fastest tests used to evaluate the heart. Electrodes are placed at certain locations on the chest, arms and legs. When the electrodes are connected to an ECG machine by lead wires, the electrical activity of the heart is measured, interpreted and printed out. No electricity is sent into the body.
Natural electrical impulses coordinate contractions of the different parts of the heart to keep blood flowing the way it should. An ECG records these impulses to show how fast the heart is beating, the rhythm of the heart beats (steady or irregular), and the strength and timing of the electrical impulses as they move through the different parts of the heart. Changes in an ECG can be a sign of many heart-related conditions.
An ECG is often used:
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To look for the cause of chest pain
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To evaluate problems which may be heart-related, such as severe tiredness, shortness of breath, dizziness or fainting
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To identify irregular heartbeats
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To help determine the overall health of the heart prior to procedures such as surgery; after treatment for conditions such as a heart attack; and after heart surgery or cardiac catheterization
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To see how heart medications or an implanted pacemaker are working
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To get a baseline tracing of the heart's function during a physical exam
An exercise ECG may be done:
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To assess stress or exercise tolerance for suspected coronary artery disease (blocked arteries in the heart)
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To determine limits for safe exercise before entering a cardiac rehab program or when recovering from a cardiac event, such as a heart attack or heart surgery
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To assess heart rhythm and electrical activity during exercise
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To evaluate heart rate and blood pressure during exercise