BSIP VEM / SCIENCE PHOTO LIBRARY BSIP VEM / SCIENCE PHOTO LIBRARY
Healthy ECG heart trace. Electrocardiogram (ECG) trace of a healthy heartbeat. The heart is a hollow muscle that pumps blood around the body. ECG traces measure the beating of the heart as a series of waves of various sizes. These waves correspond to the electrical activity of the heart muscle just before it contracts. The tall wave corresponds to contraction of the heart's lower chambers, the ventricles. The small wave just before this peak corresponds to contraction of the upper chambers, the atria. The medium wave occurs as the heart's electrical potential returns to normal. An ECG is an important means of monitoring the heart and diagnosing heart diseases.
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