The Heart Pump
Your heart is constantly pumping. The heart pumps at different speeds and patterns. This is called your heart rhythm. An abnormal heart rhythm is called an "arrhythmia." Some arrhythmias are common and some are life-threatening. An arrhythmia can be a slow heart rate or a fast heart rate.
First, let's look at how the heart works. The heart is a muscle and contains four chambers. The two upper chambers (atria) receive blood from the body and lungs. The two lower chambers (ventricles) contract and push blood to the body and lungs.
As the heart contracts, the four chambers work together to provide blood to the body.