Harvard Heart Letter

Ask the doctor: How is atrial flutter different from atrial fibrillation?

Ask the doctor

How is atrial flutter different from atrial fibrillation?

Q. What are the differences between atrial flutter and atrial fibrillation?

A. Atrial flutter and atrial fibrillation are abnormal rhythms involving the upper chambers of the heart (the atria). As such, they're both classified as supraventricular arrhythmias. Both cause the atria to beat far faster than they should. The big differences are in their causes and patterns.

Atrial fibrillation is usually caused by a barrage of uncoordinated electrical signals that trigger cells in the atria to contract independently of one another. The atria themselves don't actually contract because the individual heart muscles aren't synchronized. The result is a fast and irregular rhythm. Atrial flutter, in contrast, is a fast and regular rhythm caused by a small, tight circle of electrical activity. Every time the wave of excitement goes around the loop, the atria contract. The term "atrial flutter" comes from the fact that when it is occurring, the edges of the atria look like the flapping wings of a bird.

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