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Atrial Fibrillation–Key Facts

It can Cause Dangerous Heart Rate or Just be an Inconvenience

Oct 27, 2008 James Cooper

Atrial fibrillation is the most common potentially life threatening abnormal heart rhythm, but often it's nothing more than a condition that needs little concern.

Michael, a 64 year old man, ran his usual Saturday morning route. “I don’t really run, I just walk-run,” he explained. When he finished, his heart beat was fast. He expected that because of the run, but the rate didn’t slow down, and seemed irregular. He had no pain or trouble breathing, so he didn’t think much of it. Back home, he mentioned it to his wife, a nurse. She took his pulse, and said, “I think you have atrial fibrillation,” and drove him to the Emergency Room.

Indeed, he did have atrial fibrillation. A number of tests were ordered, and medication was started in his vein. Within an hour, his heart beat had returned to normal. Ultimately, the heart specialist prescribed pills, and Michael went on with his life as before. Sometimes, though, atrial fibrillation is not so friendly.

What Is “Atrial?”

Atrial refers to the atrium (plural: atria). There are two linked atria at the top of the heart. They’re like anterooms leading to the larger, more robust chambers, the ventricles. The atria have two important characteristics.

Pumping. Blood coming to the heart collects in the atria. Before the ventricles contract to pump blood out of the heart into arteries, the valves open between the atria and the ventricles, and the atria contract to force a large gulp of blood into the ventricles. That priming action improves heart pumping efficiency.

Electrical. The pumping action of the atria is associated with a wave of electrical action that finds its way to the ventricles, causing them to fire (contract).

An older term for "atrial" is "auricular."

What Is “Fibrillation?”

Fibrillation is uncontrolled electrical activity. Fibrillating atria are not capable of contracting in an orderly way, so they have no meaningful pumping action.

What’s the Risk of Atrial Fibrillation?

As it suggests, atrial fibrillation is a condition in which the atria are fibrillating. The uncontrolled electrical activity is like microscopic lightening buzzing around incoherently. As it passes near a channel to the ventricles, it can spark an impulse that “ignites” or starts the ventricles to contract. The fibrillating atrial electric activity can do this many times a minute, driving the ventricular contraction rate very high—so high, that the contractions become useless, the ventricles can’t pump blood effectively, blood doesn’t flow in the arteries to the rest of the body, and the person dies.

That’s the worst case scenario. Sometimes the heart rate is very fast, and blood flow is reduced, but maintained enough to allow life to continue, as long as there are not large demands placed on the heart. And sometimes, the heart has built in protection, so the rate doesn’t get fatally high, or even in the very high range.

Another risk is the formation of blood clots in the atria. Blood swirling around in the fibrillating atria has a tendency to clot. The clot may stick to the atrial wall and bits may break off, ride the blood stream, and end up in the brain, clogging a small artery and causing a stroke.

How is Atrial Fibrillation Treated?

Michael’s atrial fibrillation was paroxysmal—it happened for only a short time. He had no other heart abnormalities, and was relatively young. He was only placed on a common daily medication.

DC Shock

If Michael’s atrial fibrillation had persisted, his doctors would have talked to him about electrical conversion, a blast of DC electric current to stun the atria, with the expectation the atria would recover back to normal rhythm.

Anticoagulation

If electrical conversion wasn’t right for him, his doctors would have talked to him about anticoagulation. The purpose of anticoagulation would be to prevent a blood clot forming in the atria, and thereby reduce the risk of a stroke. The most common medication used in the US is warfarin. Warfarin use requires careful attention to diet, and regular blood tests.

The copyright of the article Atrial Fibrillation–Key Facts in General Medicine is owned by James Cooper. Permission to republish Atrial Fibrillation–Key Facts in print or online must be granted by the author in writing.