Pacemaker

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Pacemakers

Heart Disease (Coronary Artery Disease) Slideshow

What is a pacemaker?

A pacemaker is an electronic device used to treat patients who have symptoms caused by abnormally slow heartbeats. A pacemaker is capable of keeping track of the patient's heartbeats. If the patient's heart is beating too slowly, the pacemaker will generate electrical signals similar to the heart's natural signals, causing the heart to beat faster. The purpose of the pacemaker is to maintain heartbeats so that adequate oxygen and nutrients are delivered through the blood to the organs of the body.

What is the normal function of the heart?

The heart is an organ consisting of four chambers that pump blood. The two upper chambers are called the right and left atria, and the two lower chambers are called the right and left ventricles. The right atrium receives venous blood (oxygen-poor blood) from the body and pumps it into the right ventricle. The right ventricle pumps the oxygen-poor blood to the lungs to receive oxygen. The oxygen-rich blood from the lungs then travels to the left atrium and is pumped by the left atrium into the left ventricle. The left ventricle delivers the oxygen-rich blood to the rest of the body. In addition to oxygen, the blood transports other nutrients (glucose, electrolytes, etc.) to the organs. In order to keep a body healthy, the heart must maintain an adequate heartbeat (heart rate) so that sufficient amount of oxygen and nutrients are delivered by the left ventricle to the body.

The heartbeat (heart rate) is normally governed by the frequency of electrical signals which are generated by the heart's natural pacemaker called the SA node. The SA node is located on the wall of the right atrium. Electrical signals from the SA node travel along special conduction tissues on the walls of the atria, causing the atria muscles to contract and pump. These same electrical signals then travel to the AV node, a small area in the heart that serves as an electrical relay station between the atria and the ventricles. From the AV node, these electrical signals travel along special conduction tissues to reach the walls of the ventricles, causing the ventricles to pump.

Normally, the heart can vary the amount of blood delivered to the body by varying the frequency of the signals originating from the SA node. When a person is resting and the oxygen consumption of the body is low, the frequency of signal generation by the SA node decreases, thus slowing the heart rate. During exercise or excitement, the frequency of signal generation by the SA node increases and the heart rate accelerates.