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Pacemakers and ICDs: A Patient Guide

These electronic medical devices monitor heart rhythm and deliver appropriate electrical therapy when certain arrhythmias occur. Pacemakers and ICDs can be effective in extending and improving the lives of heart patients. Millions of people are affected by arrhythmias, which contribute to about 500,000 deaths each year in the US.

What are artificial pacemakers?

An artificial pacemaker stimulates a programmed and appropriate heartbeat in patients who have a slow heart rate. The pacer is a device that is made up of a battery-powered generator that sends signals to the heart through wires that are connected to the heart . The pacer senses heartbeats and fires a stimulus back to the heart if the beats that it senses do not come at the appropriate time. A pacemaker therefore detects  heartbeats that are too slow or irregular and provides electrical signals that tell the heart to beat at a proper rate by delivering signals to the appropriate chambers of the heart.

Pacemakers are surgically implanted beneath the skin, usually just below the collarbone. Many pacemakers are programmed to lie dormant for as long as the heart is beating at a steady rate above 50 to 70 pulses per minute. Should the rate slow beyond a certain rate, the pacer will fire and raise the heart rate.

What is an implantable cardioverter defibrillator (ICD)?

Somewhat more complex than pacemakers, ICDs are devices that monitor the heart constantly, but only initiate an electrical signal when it detects a prespecified rhythmic abnormality that is dangerous. ICDs can function as pacemakers for slow heart rates, but may also deliver high-energy electrical therapy for certain fast heart rates, called defibrillation shocks The increases in heart rate that are normal with exercise should not cause firing). Surgically implanted like a pacemaker, an ICD is a miniature (but internal) version of the shock paddles used by paramedics and emergency room doctors.

Who needs an artificial pacemaker?

A natural pacemaker in the heart called the sinus node controls normal heartbeat. An electrical signal is generated by the sinus node, a group of special cells in one of the upper chambers of the heart, called the atria. The signal spreads through the heart to the lower chambers, called the ventricles, and causes the heart to beat.

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