What is a pacemaker?

A pacemaker is a small battery-operated device that helps the heart beat in a regular rhythm. Traditional pacemakers have three parts: a generator, wires (leads) and sensors (electrodes). Some newer pacemakers are wireless.

It produces electrical impulses to help control abnormal heartbeats. It's implanted under the skin through a small incision on your chest just under the collarbone or sometimes in the stomach area.

The traditional pacemaker is connected to your heart through tiny wires (leads). These are implanted at the same time. The impulses flow through these wires to your heart.

The sensors (electrodes) at the end of the wires detect abnormal heartbeats and deliver electrical impulses to return your heart to its normal rhythm.

There are different types of traditional pacemakers:

  • Single-lead pacemakers use one lead usually placed in the right ventricle (the lower right chamber of your heart).
  • Dual-lead pacemakers use one lead in the right atrium and one lead in the right ventricle.
  • Biventricular pacemakers (also called cardiac resynchronization therapy or CRT) use three leads. They are placed in the right atrium, right ventricle and left ventricle.

Wireless pacemakers are smaller than traditional ones. The pulse generator and electrodes are all in one device. Placement of the pacemaker doesn't require surgery. It's placed inside your heart through a catheter (small tube) inserted through one of your veins. Once it's in place, the pacemaker sends impulses to the right ventricle.


View an animation of a pacemaker.

Why do I need one?

Your doctor may recommend a pacemaker to make your heart beat more regularly if:

  • Your heartbeat is too slow and often irregular.
  • Your heartbeat is sometimes normal and sometimes too fast or too slow.

How does a pacemaker work?

The sinus node is the heart's natural pacemaker. It's a small mass of specialized cells in the top of the right atrium (upper chamber of the heart). It produces the electrical impulses that cause your heart to beat.

A chamber of the heart contracts when an electrical impulse or signal moves across it. For the heart to beat properly, the signal must travel down a specific path to reach the ventricles (the heart's lower chambers).

When the heart's natural pacemaker is defective, the heartbeat may be too fast, too slow or irregular. Rhythm problems also can occur because of a blockage or abnormality of your heart's electrical pathways.

An artificial pacemaker replaces the heart's defective natural pacemaker functions. Most pacemakers work only when they’re needed (demand pacemakers).

  • Demand pacemakers have a sensing device. It shuts the pacemaker off if the heartbeat is above a certain rate.
  • When the heartbeat is slower than the pacemaker rate, the sensing device turns the pacemaker on again.
  • The sensors (electrodes) at the end of the wires (leads) detect abnormal heartbeats and deliver electrical impulses to return your heart to its normal rhythm.

Download and print our Answers by Heart sheet: What is a Pacemaker? (PDF)

Learn about devices that interfere with a pacemaker.

Also learn what you can and cannot do when you have a pacemaker. Read about living with a pacemaker.