Sunday, May 21, 2017

Atrial fibrillation begets Atrial fibrillation: Explanation

Hi ! Short post on pathophysiology of Atrial Fibrillation!

- Atrial Fibrillation is a fairly common disorder of rhythm, where the atria begin to beat at random , irregular and very high rates. Like 300-600 beats / min !
- Some of these MANY contractions get transmitted to the ventricles causing an Irregular , yet High , Ventricular rate - around 100-160 per minute or even higher.

Now how this occurs is a very interesting yet much-ignored mechanism.

- Due to some pre existing factors like Rheumatic heart disease , Myocardial ischemia or Thyroid abnormalities among many others, the atria get electrically irritated and begin to fire on their own.

- These ectopic foci are common along the opening of the pulmonary veins = called the pulmonary sleeve.
This area of hyperactivity and automaticity begins to fire from the left Atrium creating a wavefront of abnormal impulses.

- Say one of these myocytes becomes ectopic one day and produces an abnormal wavefront. This wavefront progresses across the atrium and in turn stimulates the other Atrial myocytes to inturn fire ectopically -- causing formation of multiple Daughter ectopic foci.

- These daughter ectopic foci produce daughter wavelets that then propagate through the atria , in turn producing more duaghter wavefronts.

- Eventually there are A LOT of Atrial foci causing multiple wavelets to produce multiple electrical wavefronts.

- Thus A-Fib causes multiple wavefronts which in turn cause more wavefronts eventually propogating A fib as a positive feedback mechanism​.

- In the long term, due to this constant irregular beating there is fibrosis and electrophysiological remodelling making the atrium more irritable and automatic.

Thus A-Fib begets A-Fib!

Hope you liked this !
Happy Studying !
Stay awesome.
~A.P.Burkholderia

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