What is an arrhythmia?
Arrhythmias (or dysrhythmias) are abnormal rhythms of the heart, which cause the heart to pump less effectively.

Normally, as the electrical impulse moves through the heart, the heart contracts -- about 60 to 100 times a minute. Each contraction represents one heartbeat. The atria contract a fraction of a second before the ventricles so their blood empties into the ventricles before the ventricles contract.

Under some conditions almost all heart tissue is capable of starting a heartbeat, or becoming the pacemaker. An arrhythmia occurs when:

• the heart's natural pacemaker develops an abnormal rate or rhythm

• the normal conduction pathway is interrupted

• another part of the heart takes over as pacemaker

What is atrial fibrillation?
Atrial fibrillation is a type of arrthymia. With atrial fibrillation, the electrical signals in the atria (the two small chambers of the heart) are fired in a very fast and uncontrolled manner. The atria quivers instead of beats. The electrical signals then arrive in the ventricles in an irregular fashion.

How Your Heart Beats

The following electrical heart conduction pathway must be followed to ensure the heart pumps properly.

• the heartbeat starts in the right atrium when a special group of cells (the sinus node or "pacemaker" of the heart) sends an electrical signal

• the signal spreads throughout the atria and to the atrioventricular (A-V) node

• the A-V node connects to a group of fibers in the ventricles that conduct the electric signal

• the impulse travels down these specialized fibers to all parts of the ventricles

Aspirin, warfarin, and cardiac medications may be used to treat atrial fibrillation.

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