A normal heart beat begins with an electrical impulse in the top chamber of the heart (atria), which spreads across both the right and left atria causing these chambers to contract, propelling blood forward into the main pumping chambers of the heart (ventricles). The electrical impulse subsequently spreads to the ventricles, which then contract and pump blood to the body. A normal heart rhythm maintains synchronous heart contractions, propelling blood throughout the body most effectively.
Atrial fibrillation is a very rapid and chaotic rhythm occurring in the top chambers of the heart, during which the electrical impulses appear to come from everywhere at the same time. During atrial fibrillation, the atria do not contract synchronously. This allows for momentary blood pooling and stasis, during which time blood clots may form. These blood clots may then be pumped throughout the body and to the brain, causing stroke. It is blood clot formation in the atria during atrial fibrillation that accounts for strokes due to atrial fibrillation. During atrial fibrillation, rapid and irregular impulses are transmitted to the bottom pumping chambers, resulting in an overall heart rate rhythm that is also rapid in and irregular, albeit slower due to a filtering mechanism between top and bottom chambers.
Atrial fibrillation is classified as paroxysmal if episodes last less than 7 days, and persistent if episodes last longer than 7 days. Atrial fibrillation is classified as longstanding if episodes last beyond 12 months, and permanent if no further attempts to achieve normal rhythm are
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