Atrial fibrillation is a cardiac arrhythmia, more commonly known as AFib. This is one of the supraventricular tachycardias. In a normal heart, the wavelengths of the electric waves are transferred from the SA node to the AV node in an organized manner.
Once there is an organized conduct, passing from the SA node to the AV node, then it will be obtained concentrated or uniform conduction of atrial tissue. But with AFib, the wavelengths are a mess. Notice how fickle they are and go everywhere.
Because this organized signal is lost, there will be no single abbreviation of the atria, instead, with these intermittent waves, there will be atrial spasms. In fact, it looks like there is a bag worms in the atria and they all move around, if you can imagine it. Also, the waves are doing their job, so they will signal the AV node intermittently, and this will lead to an irregular heartbeat, due to intermittent stimulation.
They say that the classic ECF of AFib is incorrectly inconstant. What does this mean? Notice how the distance between RR intervals are different with each stroke.
In a normal heart, there are evenly spaced RR intervals. With AFib there are different distances between R and R intervals. Also with AFib, no distinct P waves are seen on the ECG. Instead, these rough deformed lines are visible. But there are no distinct P-waves because, you remember, the atrium gets a spasm.
So it won't work out uniform concentric contraction of the atria, and instead there will be these rough deformed lines, which represent atrial spasm. What are the risk factors for atrial fibrillation? Anyone who has diseased atrial tissue, there is an increased risk of AFib.
How does atrial tissue get sick? With age, as the skin of the body it ages, so the atrial tissue ages. Also, anything that drives the atrial tissue to become inflamed may cause atrial fibrillation. Imagine that someone just had a heart procedure, which causes inflammation, this will increase his risk of atrial fibrillation and everything which causes atrial enlargement. This includes years of high blood pressure, as well as certain types of valve diseases, such as mitral stenosis, certain types of lung disease, as well as a previous AFib, may enlarge the atria.
Other things that increase the risk include abnormalities of certain hormones, in particular, thyroid hormone, and also years of alcohol abuse. It is worth mentioning that people with AFib, have a higher risk of stroke.
These people are usually put on some kind of blood thinner. Why do these people have an increased risk of stroke? When the atria are in spasm, the blood will swims in the atrium. When the atrial tissue is in spasm, the blood stagnates in the atria and does not move.
What happens to blood that doesn't move? It's clotting. Imagine I'm drawing a big clot right here, imagine that if this clot comes out of the atrium, reaches the ventricle and exits in the rest of the bloodstream, it can reach other organs, including the brain.
And if a clot reaches a blood vessel that feeds brain, this can lead to a stroke. Therefore, people who have AFib usually are placed on blood thinners that will help prevent clot formation and, therefore, will reduce the risk from certain types of strokes.
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