What is a pacemaker?

A small battery-operated device that helps the heart beat in a regular rhythm. There are two parts: a generator and wires (leads). View an animation of a pacemaker.

• The generator is a small battery-powered unit.
• It produces the electrical impulses that stimulate your heart to beat.
• The generator may be implanted under your skin through a small incision.
• The generator is connected to your heart through tiny wires that are implanted at the same time.
• The impulses flow through these leads to your heart and are timed to flow at regular intervals just as impulses from your heart's natural pacemaker would.
• Some pacemakers are external and temporary, not surgically implanted.

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 it work?

It replaces the heart's defective natural pacemaker functions.

• The sinoatrial (SA) node or 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 of your heart's electrical pathways.
• The pacemaker's pulse generator sends electrical impulses to the heart to help it pump properly. An electrode is placed next to the heart wall and small electrical charges travel through the wire to the heart.
• Most pacemakers have a sensing mode that inhibits the pacemaker from sending impulses when the heartbeat is above a certain level. It allows the pacemaker to fire when the heartbeat is too slow. These are called demand pacemakers.