The Mechanics of Atrial Fibrillation

What is atrial fibrillation?
We asked Dr. Mitchell Faddis, a Washington University
cardiac electrophysiologist at Barnes-Jewish Hospital to explain how a-fib occurs. Atrial fibrillation is a very common condition
that affects the heart and causes it to beat irregularly
and often very rapidly. It’s associated with blood clots that
form in the heart and can cause stroke as well as other heart conditions –
in particular, heart failure. Atrial fibrillation contributes to
about a third of all strokes that occur. The heart is an electrical organ where
an electrical signal flows smoothly from the top of the heart down to the bottom. Atrial fibrillation causes
changes in the heart. Atrial fibrillation tends to form in
the left upper chamber or left atrium. When the pressure on the
left atrium is too high, it expands just like a
balloon that’s over-inflated. The body grows scar tissue into the walls
of that chamber to reinforce it and to protect it against further expansion. The problem with the scar tissue is
that it’s not electrically active and it works to break up the smooth flow
of electricity through the chamber. Think of a boulder interrupting
the flow of water in a stream. Electrical signals do that in the left
atrium and eventually can degenerate into the pattern of electrical fibrillation. This fibrillation wears the heart cells
out and they become weak. Over time, the cells of that chamber are weakened and become more prone to remain in atrial fibrillation. They become more fragile, pump less blood, and eventually the atrial fibrillation
becomes more permanent in the left upper chamber and harder to treat. Certain conditions increase the risk of a-fib, including hypertension, sleep apnea, and diabetes. Now, hypertension is a condition where the
heart has to push against the blood pressure to pump the blood around
the body. As a result of that, the muscle in that chamber
gets thicker and thicker. Think of a weight lifter whose muscles
get denser in response to their training. Unfortunately, that’s not
a good thing in the heart. Sleep apnea is a very common condition where patients repeatedly stop breathing through the night. Those bouts of very high blood pressure
happen over and over and the left atrium experiences the same condition as in
hypertension or high blood pressure. Other conditions that contribute to a-fib
are diabetes with elevated blood sugar or blood glucose and obesity. All of these conditions are treatable by
treating the underlying conditions that give rise to atrial fibrillation. We can protect patients. With an accurate diagnosis, a-fib is treatable and normal
heart rhythm can be restored. If you think that you or a loved one
may be at risk for a-fib, visit BarnesJewish.org/afib to learn more.

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