SOVEREIGN, ISM / SCIENCE PHOTO LIBRARY SOVEREIGN, ISM / SCIENCE PHOTO LIBRARY
Irregular heartbeat. Electrocardiogram (ECG) of electrical activity (yellow traces) in a man's heart in a case of auricular extrasystole. Two of the six ECG traces are shown here. An extrasystole is an extra, or irregular heartbeat, and here is affecting the heart's upper chambers (atrial, or auricular). The extra heartbeat is seen as one of the two beats very close together at left. Irregular heartbeats can be treated with drugs (such as beta blockers) or pacemakers to maintain the heart's normal rhythm. An ECG is obtained by using electrodes to detect the electrical activity of the heart.
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