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Understanding Rhythms

Understanding Rhythms

Atrial Fibrillation

Atrial fibrillation(A-Fib or AF) is the most common type of heart rhythm disorder, or arrhythmia. It means, literally, that the atria (the upper chambers of the heart) are fibrillating (quivering rapidly and chaotically), rather than beating in their normal, rhythmic pattern.

AF is caused by a problem with the electrical signals that coordinate the muscles of the atria. When these signals misfire, the atria respond in an uncontrolled, uncoordinated manner. This throws off the normal rhythm between the upper and lower chambers of the heart. (In atrial flutter, a similar condition, the atria also beat too quickly and disrupt the normal rhythm, but the electrical pattern in atrial flutter is more organized and predictable.)

While AF is not immediately life threatening, it does make the upper chambers less effective at pumping blood to the lower chambers of the heart. This can cause stagnant blood to pool in the nooks and crannies of the atria, which increases the risk of forming blood clots that could lead to a stroke. Without treatment, AF can also cause a fast pulse rate for a prolonged period, which can weaken the ventricular heart muscle over time, and lead to heart failure. 


  • In some people, AF causes no obvious symptoms. In others, it may cause uncomfortable symptoms such as:

  • Shortness of breath

  • Palpitations

  • Difficulting exercising

  • Chest discomfort

  • Dizziness or fainting

Episodes of AF may come and go (this is called paroxysmal AF). Over time, they may last longer and become more persistent, requiring medication or electrical treatment to stop them. Longstanding persistent AF is less responsive to treatment and may require more extensive medical intervention in order to restore a normal rhythm.


Risk factors for developing AF

Although some people get AF without any apparent cause, people with any of these risk factors are more likely to develop AF:

  • Diabetes

  • High blood pressure

  • Coronary artery disease

  • Mitral valve disease

  • Thyroid disease

  • Chronic lung disease

  • Prior open heart surgery

  • Sleep apnea

  • Excessive alcohol or stimulant use

  • Age over 60

  • Obesity

Because AF is a disorder of the heart’s electrical system, it is diagnosed by recording the electrical activity of your heart, using an eletrocardiogram (ECG, or EKG). The ECG is painless and requires no incisions or needles. A technician will attach electrodes (like small bandages) to your skin. The electrodes connect to a machine that helps analyze your heart’s electrical activity. For a longer study, you may be asked to wear a portable monitor (about the size of a pager) at home to record your heart’s rhythm over a period of days. A more invasive electrophysiology (EP) study may be necessary in some cases to make a diagnosis and discover the specific type of arrhythmia that is causing symptoms.

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