Health Conditions

What causes it?

The heart muscle has four chambers or compartments. The two upper chambers are called the right and left atria. Within the right atria, is a small mass of tissue - known as the sinoatrial node (SA node). This SA node triggers an electrical - like impulse that stimulates the heart muscle to beat and pump blood in and out of the heart. The SA node is like a ?pacemaker? for the heart. It controls how fast the heart beats and keeps the rhythm of the heart regular.

For most individuals, when the heart beats at a normal rate and rhythm, it pumps about 60 to 100 times per minute. Atrial Fibrillation (AF) can cause the heart to beat 120 to 180 times per minute, or faster. When AF occurs, electrical impulses originate from many areas in the atrium instead of from the SA node - as many as 350 different impulses per minute, all trying to cause the heart to beat. Unfortunately, the heart cannot respond to the overload of electrical - like impulses and thus it begins to beat rapidly and irregularly - almost like a quiver instead of a beat. The fast and irregular beating of the heart can cause the feeling of heart fluttering or palpitations. Additionally, blood is not pumped effectively and may pool in the atria. When blood pools, it is more likely to clot. If a clot develops and breaks loose it can clog a blood vessel in the brain, causing a stroke.

The two lower chambers - the right and left ventricles - of the heart are also affected by AF. Rapid and irregular beating does not allow sufficient time for the ventricles to adequately fill with blood before being stimulated to pump the blood out of the heart again. As a result, less blood is pumped out of the heart and the body?s tissues--which are dependent on the heart for oxygen-rich blood--are provided with a smaller supply, causing symptoms like shortness-of-breath, dizziness and fatigue or tiredness.