Science Illustrated

You Can Restart A Heart With A Defibrilla­tor

The heart beats in a nicely coordinate­d rhythm. If it falls out of step, the rhythm could be restored with a shock.

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The shock from a defibrilat­or’s electrodes is so powerful that it makes a lifeless body jerk, but the device’s electricit­y will only revive a patient if his heart still includes certain electrical activity, that is, it has not entirely stopped.

Heartbeats are powered by regular electrical impulses that pass through the organ’s millions of muscle cells, making them contract. The impulses usually begin in a small knot in the right ventricle of the heart, from where they spread to the rest of the organ. If the cells of the knot lose their rhythm, the flow of blood is disrupted.

One of the most well-known types of disruption makes the heart beat 200+ times per minute, losing its ability to pump blood efficientl­y about the body. The disruption could develop into ventricula­r fibrillati­on, by which the heart "quivers" up to 400 times per minute, not pumping any blood about the body at all.

Some types of disruption can be cured with a powerful shock from a defibrilla­tor, resetting the cells of the small heart knot to the old rhythm again. Other types of disruption are so complex that it is impossible to save the patient.

 ??  ?? Normal cardiac rhythm Doctors only send power through a heart, if it is still active.
Normal cardiac rhythm Doctors only send power through a heart, if it is still active.

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