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  • Atrial fibrillation is the most common type of cardiac arrhythmia. In a healthy heart,

  • the sinoatrial node or SA node initiates all electrical impulses in the atria. In atrial

  • fibrillation, electrical impulses are initiated randomly from many other sites called ectopic

  • sites in and around the atria, commonly near the roots of pulmonary veins. These un-synchronized,

  • chaotic electrical signals cause the atria to quiver or fibrillate rather than contract.

  • Although the atrial rate during atrial fibrillation can be extremely high, most of the electrical

  • impulses do not pass through the atrioventricularthe AV - node to the ventricles. This

  • is due to refractory properties of the cells of the AV node. Those that do come through are

  • irregular. Ventricular rate or heart rate is therefore irregular and can range from

  • slow - less than 60 - to rapid -more than 100 - beats per minute.

  • On an ECG, atrial fibrillation is characterized by absence of P-waves and irregular narrow

  • QRS complexes. Reminder: P-wave represents electrical activity of the SA node that is

  • now obscured by activities of multiple ectopic sites. The baseline may appear undulating

  • or totally flat depending on the number of ectopic sites in the atria. In general, larger

  • number of ectopic sites results in flatter baseline.

  • As the atria do not function properly, the heart puts out less blood, and heart failure

  • may occur. The most common complication of atrial fibrillation, however, is the formation

  • of blood clots in the atria. As the atria do not empty completely into the ventricles,

  • the blood may stagnate inside the atria and blood clots may form. These clots may then

  • pass into the bloodstream, get stuck in small arteries and block them. When a blood clot

  • blocks an artery in the brain, a stroke may result.

Atrial fibrillation is the most common type of cardiac arrhythmia. In a healthy heart,


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    alex 發佈於 2021 年 01 月 14 日