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What Is a Pacemaker?

Each individual heartbeat is actually a collection of several muscle movements spurred into action by electrical impulses.

The first electrical signal comes from the heart’s own natural pacemaker, the sinoatrial node, comprised of electrically active cells and located in the upper right heart chamber. This node sends a steady stream of electrical signals along a pathway through the heart’s upper chambers. The signals then travel to the electrical bridge – the atrioventricular node – between the upper and lower chambers and, finally, move to the lower chambers.

A problem at any point in the electrical pathway can wreak havoc with the regular beating of a heart. Luckily, an artificial pacemaker – a small, battery -operated device – can take over the role of the heart’s own electrical system, if necessary.

Although it weighs just about an ounce, a pacemaker contains a powerful battery, electronic circuits and computer memory that together generate electronic signals. The signals, or pacing pulses, are carried along thin, insulated wires, or leads, to the heart muscle. The signals cause the heart muscle to begin the contractions that cause a heartbeat.

A pacemaker is implanted just below the collarbone in a procedure that takes about two hours. It is programmed to stimulate the heart at a pre-determined rate, and settings can be adjusted at any time. Routine evaluation, sometimes even via telephone, ensures the pacemaker is working properly and monitors battery life, which generally runs from five to ten years.

 

 

The Heart's Electrical System

Your heart has its own internal electrical system that controls the speed and rhythm of your heartbeat. With each heartbeat, an electrical signal spreads from the top of the heart to the bottom. As it travels, the electrical signal causes the heart to contract in an organized manner and pump blood.

 

Electrical signals normally begin in a group of cells called the sinus node. As these signals spread from the top to the bottom of the heart, they coordinate the timing of heart cell activity. First, the two upper chambers of the heart, called atria, contract. This contraction squeezes blood into the lower chambers of the heart, which are called ventricles. The ventricles then contract and send blood to the rest of the body. The combined contraction of the atria and ventricles is a heartbeat.

 

For more information about the heart's electrical system and how a healthy heart works, see the Diseases and Conditions Index article on How the Heart Works.

 

Overview

Faulty electrical signaling in the heart causes arrhythmias. A pacemaker uses low-energy electrical pulses to correct faulty electrical signaling. Pacemakers can:

 

 

 

 

 

 

 

Pacemakers also can monitor and record your heart's electrical activity and the rhythm of your heartbeat. Newer pacemakers can monitor your blood temperature, breathing rate, and other factors and adjust your heart rate to changes in your activity.

 

Pacemakers can be temporary or permanent. Temporary pacemakers are used to treat temporary heartbeat problems, such as a slow heartbeat due to heart attack, heart surgery, or an overdose of medicine. Temporary pacemakers are used in emergencies until a permanent pacemaker can be implanted or until the temporary condition goes away. A person with a temporary pacemaker will stay in the hospital as long as the pacemaker is in place.

 

In this article, "pacemakers" refers to permanent devices, unless stated otherwise.

 

Doctors also treat arrhythmias with another device called an implantable cardioverter defibrillator (ICD). An ICD is like a pacemaker in some ways, but it can use higher energy electrical pulses to treat certain dangerous types of arrhythmia.

 

For more information on ICDs, see the Diseases and Conditions Index article on Implantable Cardioverter Defibrillator.