Pacemaker

Home » Pacemaker » Overview

Overview

Pacemakers are battery-powered implantable devices that function to electrically stimulate the heart to contract and thus to pump blood throughout the body. Pacemakers consist of a pager-sized housing device which contains a battery and the electronic circuitry that runs the pacemaker, and one or two long thin wires that travel through a vein in the chest to the heart. Pacemakers are usually implanted in patients in whom the heart's own "spark plug" or electrical system is no longer functioning normally.

The Heart and Its Electrical System
In order to better understand why some patients require pacemakers and how these devices work, it is worth briefly discussing how the heart and its electrical system work. The heart is divided into right and left sides. Each side has a chamber that receives blood that is returning to the heart (called atria) and a muscular chamber that is responsible for pumping blood out of the heart (called ventricles).

Blood that has traveled to parts of the body and is now oxygen-poor returns to the heart and enters the right atrium. This blood is then pumped by contraction of the right atrium into the right ventricle. The right ventricle, in turn, contracts and pumps this blood to the lungs, where it absorbs oxygen. The oxygen-rich blood then returns from the lungs to the heart and enters the left atrium, where it is pumped into the left ventricle. The left ventricle is the most muscular of the heart's four chambers and serves as the main pumping chamber of the heart. When the muscular tissue of the left ventricle contracts, blood is pumped into the aorta, the main artery of the body which supplies blood to other arteries. Oxygen-rich blood travels through the aorta to other arteries of the body and then, in turn, to the organs and tissues of the body, which require oxygen to function. Oxygen-poor blood returns from these organs and tissues through the veins back to the right atrium of the heart, and the cycle repeats itself.

The contractions of the different chambers of the heart are normally organized in a very specific manner—a special type of electrical impulse travels through the heart and sets off contractions in the chambers as it passes through the chambers. Figure 2 shows the normal sequence by which this electrical impulse travels through the heart.

The heart's normal "spark plug" is an area of specialized heart tissue called the SA node, which is located in the right atrium. Each time this tissue "fires," an electrical impulse is generated that travels first through the right and left atria, signaling these chambers to contract and pump blood into the ventricles. The impulse then travels down into another small patch of specialized heart tissue called the AV node, which is located between the atria and the ventricles. The electrical impulse is conducted through the AV node and then through specialized wire-like pathways into the ventricles, where it signals the ventricles to contract and to pump blood out into the lungs and throughout the body. This normal sequence of electrical activation of the chambers of the heart is called sinus rhythm. It occurs each time the heart beats, usually about 60 to 80 times every minute.

Pacemaker Resources

	Join Our Pacemaker Forum Do you have a question, want to share medical advice, or just need to discuss your situation with someone else having a similar experience? The healthchannels forum is a resource for everyone to share and discuss their health and medical needs with others.	Advertising Disclaimer
	Living with...Share your story Do you have a personal health story that you would like to share with others? As a source of free patient education, our goal is to provide our users with trustworthy information and support from others. That's why we've started our "Living with..." sections.
	Our "Living With..." support pages are a place to share experiences about living with a certain condition, disease, disorder, or illness and for loved ones of those dealing with health-related issues. Many people, especially when newly diagnosed, find comfort in knowing that others are having a similar experience. Help others by sharing your story. View stories already submitted.
	Stay Updated Sign up for our newsletter and receive important updates on the medical conditions that are most important to you.
Are you interested in becoming a nurse? Take this test. Advertising Disclaimer To quickly access health information from your website's browser, download Healthcommunities.com's healthchannels toolbar. Advertising Disclaimer