Atrial Fibrillation

         Basic Facts

  • Atrial fibrillation is an arrhythmia, a disturbance in the heart's rate or rhythm.
  • In atrial fibrillation, the electrical signal that normally causes the atria (the heart's upper chambers) to contract in an organized fashion circles through the muscles of the atria in an uncoordinated manner. This causes the atria to quiver, sometimes more than 600 times per minute, without contracting. At the same time, this might drive the rate of the lower chambers of the heart (ventricles), resulting in an irregular fast heart rate.
  • Left untreated, AF can lead to cardiomyopathy (enlarged heart), heart failure, or stroke.

For a healthy heart, every heartbeat starts in the atria (the heart's upper chambers) and moves into the ventricles, the heart's lower chambers, stimulating them to contract. Normally, the atria and the ventricles contract in this coordinated manner, and a normal heart beats between 60 and 100 times per minute. 

In AF, the electrical signal that normally causes the atria to contract in an organized fashion circles through the muscles of the atria in an uncoordinated manner. This causes the atria to quiver, sometimes firing more than 600 times per minute without contracting. At the same time, this might drive the rate of the lower chambers of the heart (ventricles), to go faster than normal, resulting in an irregular fast heart rate. In addition, the activity of the sinus node, which usually initiates every heartbeat, is overridden, which can cause the ventricles to beat irregularly.

There are three types of AF:

  • Intermittent (paroxysmal),
  • Persistent, and
  • Permanent/chronic.
One significant danger of AF is that blood clots (called thrombi) can form during an episode of AF, enter the bloodstream, and lodge in the brain, causing a stroke. Uncontrolled AF can weaken the heart, which may lead to dilated cardiomyopathy or heart failure.

Atrial Fibrillation FAQ