VANDERBILT UNIVERSITY MEDICAL CENTER

Vanderbilt Heart

The Electrical System and Arrhythmia

A healthy heart has a regular beat. This rhythmic contracting (beating of the heart) is controlled by an electrical system that sends electrical signals throughout the heart. Click here to see how it works.

The normal electrical signal begins in the upper part of the right atrium (upper heart chamber). It starts in a group of tissue called the sinus node (SA node). The SA node starts the heartbeat. The SA node sets the speed and rhythm of your heart and works as a natural pacemaker. The electrical activity spreads from the sinus node through the atria (the two upper heart chambers), causing them to contract.
 
The signal then passes down to the two lower chambers of the heart (ventricles) by way of the sinoatrial node (AV node). The AV node slows down the electrical signal and lets the atria contract before the ventricles so the blood pumps correctly to each chamber. Special pathways in the ventricles carry the signal from the AV node throughout the larger muscle tissue of the ventricles, causing both ventricles to contract at the same time and pump the blood to the rest of the body.

Problems with the electrical system of your heart are commonly known as arrhythmia.

If the electrical system of your heart is diseased, injured or not developed in the usual way, you may have an arrythmia. Arrhythmias come in two: groups.

Fast heart rhythms are called tachycardias. Tachycardia is a heart rhythm that beats more than 100 times per minute. A tachycardia may begin in the atria (upper heart chambers), the sinoatrial node (AV node) or in the ventricles (lower heart chambers). Because the ventricles are responsible for pumping blood to the lungs and the body, fast heart rhythms in the ventricles are generally more serious.

Bradycardia is a slow heart rate, less than 60 beats per minute. When you suffer from bradycardia, your sinus node, which starts  each normal heartbeat, fails to trigger the electrical signals as it should. It may not start the heartbeat often enough, it may skip or miss some of the heartbeats, or it may send too many heartbeats. The heart may beat too slowly, or it may alternate between too slow and too fast.

Click here to learn more about arrythmia, including symptoms and treatments.

Find Us On:
YouTube Twitter Facebook