Atrial Fibrillation

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.

How does the physician know what an EKG means?

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Almost everyone knows what a basic EKG tracing looks like. But what does it mean?

• The first little upward notch of the EKG tracing is called the "P wave." The P wave indicates that the atria (the 2 upper chambers of the heart) are contracting to pump out blood.
  
  
• The next part of the tracing is a short downward section connected to a tall upward section. This next part is called the "QRS complex." This part indicates that the ventricles (the 2 lower chambers of the heart) are contracting to pump out blood.
  
  
• The next short upward segment is called the "ST segment." The ST segment indicates the amount of time from the end of the contraction of the ventricles to the beginning of the rest period before the ventricles begin to contract for the next beat.
  
  
• The next upward curve is called the "T wave." The T wave indicates the resting period of the ventricles.

When your physician studies your EKG, he/she looks at the size and length of each part of the EKG. Variations in size and length of the different parts of the tracing may be significant. The tracing for each lead of a 12-lead EKG will look different, but will have the same basic components as described above. Each lead of the 12-lead is "looking" at a specific part of the heart, so variations in a lead may indicate a problem with the part of the heart associated with the lead.

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 quiver instead of contracts. The electrical signals then arrive in the ventricles in an irregular fashion. When the heart does not beat effectively, the blood may pool and/or clot. If a blood clot becomes lodged in an artery in the brain, a stroke (brain attack) may occur. About 15 percent of strokes occur in persons with atrial fibrillation. Aspirin, warfarin, and cardiac medications may be used to treat atrial fibrillation.

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