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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 AB 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 AB 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.
