What Is a Cardiac Arrhythmia?
Normal Heart Rhythm
The heart is made up of 2 upper chambers, called the atria, and 2 lower chambers, called the ventricles. Electrical impulses that coordinate the heart's contractions begin at the sinoatrial node—also called the sinus node or SA node.
The SA node is a bundle of highly specialized cells in the right atrium. The signal passes through the right and left atria, signaling to them to contract. When the atria contract, oxygen-rich blood flows into the ventricles. Then the atrioventricular node, or AV node, receives the signal and passes it into the ventricles, signaling to contract. When the ventricles contract, blood is pumped out of the heart into the body.
Abnormal Heart Rhythm
Sometimes, however, the flow of electrical impulses does not operate properly. The sinus node may send out signals too quickly, or it may send out too many signals. In other cases, the signals may reverberate inside one of the heart's chambers instead of moving on in a regular pattern.
The result is a fast or irregular heartbeat. It can sometimes feel like a flutter. These abnormal rhythms are called arrhythmias or cardiac arrhythmias. When the heart beats erratically, it does not pump blood as efficiently as it should, shortchanging the delivery of oxygen throughout the body and causing you to feel ill.
