Circulation

Normal Heart Rhythms

Coronary Circulation Diagram (click image to enlarge)

Your heart is a muscle that pumps blood through your body. The heart muscle beats (contracts and relaxes) many times a minute with a speed and pattern known as your heart rhythm. Signals from the heart's electrical system set the heart rhythm. If there's a problem with these signals, your heart may beat too slowly, too quickly or irregularly. Each of these problems is called an arrhythmia.

Your Heart's Pump
Your heart muscle contains four chambers that hold blood as it moves through the heart. The two upper chambers (atria) receive blood from the lungs and body. The atria contract to move blood through valves into the two lower chambers (ventricles). Then the larger ventricles contract with more force to move blood out to your lungs and body.

Your Heart's Electrical System

Your heart's electrical system creates signals that tell the chambers to contract. Electrical signals generated inside the heart tell the atria to contract to move blood to the ventricles, then tell the ventricles to contract to move blood to the lungs and body. Groups of special electrical cells in the right atrium, called nodes, create or send these electrical signals. The signals travel along pathways of special cells. In the ventricles, these pathways are called bundle branches.