A pacemaker is a small device that’s placed under the skin in your chest to help control your heartbeat. It’s used to help your heart beat more regularly if you have an irregular heartbeat (arrhythmia), particularly a slow one. Implanting a pacemaker in your chest requires a surgical procedure.
Types of pacemakers
Depending on your condition, you might have one of the following types of pacemakers.
Single chamber pacemaker. This type usually carries electrical impulses to the right ventricle of your heart.
Dual chamber pacemaker. This type carries electrical impulses to the right ventricle and the right atrium of your heart to help control the timing of contractions between the two chambers.
Biventricular pacemaker. Biventricular pacing, also called cardiac resynchronization therapy, is for people with heart failure with abnormal electrical systems. This type of pacemaker stimulates the lower chambers of the heart (the right and left ventricles) to make the heart beat more efficiently.
Why it’s done
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Pacemakers are implanted to help control your heartbeat. They can be implanted temporarily to treat a slow heartbeat after a heart attack, surgery or medication overdose. Or they can be implanted permanently to correct a slow or irregular heartbeat or, in some people, to help treat heart failure.
How your heart beats
The heart is a muscular, fist-sized pump with four chambers, two on the left side and two on the right. The upper chambers (right and left atria) and the lower chambers (right and left ventricles) work with your heart’s electrical system to keep your heart beating at an appropriate rate — usually 60 to 100 beats a minute for adults at rest.
Your heart’s electrical system controls your heartbeat, beginning in a group of cells at the top of the heart (sinus node) and spreading to the bottom, causing it to contract and pump blood. Aging, heart muscle damage from a heart attack, some medications and certain genetic defects can cause an abnormal heart rhythm.
What a pacemaker does
An implanted electronic pacemaker mimics the action of your natural electrical system. A pacemaker comprises two parts:
Pulse generator. This small metal container houses a battery and the electrical circuitry that regulates the rate of electrical pulses sent to your heart.
Leads (electrodes). One to three flexible, insulated wires are each placed in a chamber, or chambers, of your heart and deliver the electrical pulses to adjust your heart rate.
Pacemakers work only when needed. If your heartbeat is too slow (bradycardia), the pacemaker sends electrical signals to your heart to correct the beat.
Also, newer pacemakers have sensors that detect body motion or breathing rate, which signal the pacemakers to increase heart rate during exercise, as needed.
Two smaller, leadless pacemakers, which can be implanted directly into the heart, have been approved for use in the United States. Because a lead isn’t required, this device can minimize certain risks and speed recovery. Although this type of pacemaker appears to work well and safely, longer term study is needed.