A healthy heart has a regular beat. In other words, your heart muscle contracts at regular intervals. This rhythmic contracting (beating of the heart) is controlled by a special electrical system. The electrical system transmits electrical signals throughout the heart. Click here to watch a video on the electrical system of the heart.

The normal electrical signal begins in the upper portion of the right atrium (upper heart chamber). It starts in a special group of tissue called the sinus node (SA node). The SA node starts the rhythmic contraction known as the heartbeat. The SA node sets the speed and rhythm of your heart and functions as a natural pacemaker. The electrical activity spreads from the sinus node through the atria (the two upper heart chambers) causing both atria to contract.

The electrical signal then passes down to the two lower chambers of the heart (ventricles) by way of the sinoatrial node (AV node). The AV node acts as a bridge (passageway). It slows down the electrical signal and allows the atria to contract before the ventricles so the blood pumps correctly to each chamber. Special pathways within the ventricles carry the signal from the AV node very rapidly 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.