TIM VERNON, LTH NHS TRUST / SCIENCE PHOTO LIBRARY TIM VERNON, LTH NHS TRUST / SCIENCE PHOTO LIBRARY
Electrocardiogram. Hands holding an electrocardiogram (ECG) of a normal heart rate. An ECG measures the electrical activity of the heart. Contractions are caused by electrical signals between the upper (atrial) and lower (ventrical) chambers. The tall peak indicates the pumping action of the ventricles.
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