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- Atrial fibrillation is a heart arrhythmia more commonly know as AFib. It's one of the supraventricular tachycardias. In a normal heart, electrical wavelengths are conducted from the SA node to the AB node in an organized fashion. And since you have organized conduction going from the SA node to the AV node you're going to get concentric or unified contraction of the atrial tissue. However, in AFib wavelengths are in disarray. So notice how they're all erratic and going everywhere. Because you lose this organized signal, you're not going to have unified contraction of the atria, instead with these erratic wavelengths you're going to have atrial spasming. It actually kinds of looks like there's a bag of worms in the atria and they're all moving around, if you can imagine that. Also the wavelengths are doing their own things, so they're going to be signaling the AV node erratically and this is going to lead to an irregular rhythm, because of the irregular stimulation. Classically the AFib EKG is said to be irregularly irregular. What does that mean? Well notice how the distance between the R-R intervals is different with each beat. In a normal heart it's the evenly spaced R-R intervals. With AFib you have different distances between the R and the R intervals. Also in AFib there are no distinct P-waves on EKG. Instead you have the coarse squiggly lines running through. But there are no distinct P-waves, that's because remember the atria is spasming. So you're not going to get that nice unified concentric contraction of the atria, so you have these coarse squiggly lines instead representing the atrial spasm. What are the risk factors for atrial fibrillation? Well anyone that had diseased atrial tissue has an increased risk for AFib. And how does atrial tissue become diseased? Well, with old age, so the skin in your body tends to get old with age, so does your atrial tissue. Also anything that causes the tissue of the atria become inflamed can cause atrial fibrillation. So imagine if you just had a recent heart procedure that causes inflammation, that will increase your risk for atrial fibrillation and anything that causes atrial enlargement. This includes years of high blood pressure and also certain types of valve disease like mitral stenosis, certain types of lung dissease and previously having AFib can enlarge your atria. Other things that increase your risk, include certain hormonal abnormalities specifically your thyroid hormone and years of alcohol abuse. It's also worth mentioning that people who have AFib are at an increased risk for having strokes. So these people are typically put on some sort of blood thinner medication. Now why are these people at a higher risk for stroke? When the atria is spasming blood is going to pool in the atrium. When the atrial tissue is spasming, blood then pools in the atria and it doesn't move. And what happens to blood that doesn't move? It clots. Now imagine, so I'm drawing a big clot right here, and imagine if this clot escaped the atrium, went to the ventrical, and then out to the rest of the circulation, it could go to other organs, including the brain. and if a clot goes to a blood vessel that supplies the brain, well that can lead to stroke. Therefore, people who have had AFib are usually put on blood thinners which will help prevent clot formation and thereby reduce the risk of certain kinds of strokes.