atrial fibrillation
Meaning of atrial fibrillation: The two upper chambers stop beating and start quivering, and the pulse that results is irregular in a way nothing else quite copies.
Definition of atrial fibrillation
Atrial fibrillation is a heart rhythm disorder in which the two upper chambers of the heart quiver chaotically instead of contracting in an organized way. Electrical impulses fire from many points at once, and only some pass through to the lower chambers, so the pulse becomes irregular and often fast. Blood moves sluggishly in the quivering chambers and can form clots there.
What goes wrong with the signal?
A normal heartbeat starts in one place, a patch of specialized tissue in the upper right chamber, and spreads as a single organized wave. In atrial fibrillation that order collapses. Many small wavefronts circulate through the upper chambers at once, mostly arising near where the lung veins enter, and no coordinated squeeze results. The gateway between the upper and lower chambers blocks most of these signals but lets an unpredictable few through, which is why the pulse is irregular with no repeating pattern. When too many get through, the rate climbs and the rhythm becomes a form of tachycardia.
Why does it raise the risk of stroke?
Blood that is not moved along tends to clot. In a quivering upper chamber it pools, particularly in a small blind pouch off the left side, and a clot forming there sits directly in the path of blood heading for the brain. If it breaks loose it travels out with the next beats and can block an artery there. That is why an anticoagulant is central to managing the rhythm, and the decision rests on the other conditions a person has rather than on how fast or how noticeable the fibrillation is.
What are the patterns?
| Pattern | How it behaves |
|---|---|
| Paroxysmal | Starts and stops on its own, often within a day or two |
| Persistent | Continues until it is deliberately converted back |
| Long-standing persistent | Present continuously for a year or more |
| Permanent | Accepted as the working rhythm, with no further attempt to restore order |
These labels describe how the rhythm behaves over time, not how dangerous it is, and the clot risk is not lower in the intermittent forms. Detection is a separate problem. An ECG captures only what is happening while it runs, so intermittent fibrillation is often missed until a longer recording or a wearable monitor catches it. Many people feel nothing at all, and the first evidence can be a stroke or an irregular pulse noticed during an unrelated examination.
Also known as
Used in a sentence
The electrocardiogram showed atrial fibrillation with a rapid ventricular response.
Good to know
Atrial fibrillation frequently causes no symptoms and is often found during an examination arranged for something else, and the stroke risk it carries is judged from the other conditions present rather than from how fast or how troublesome the rhythm feels.
Word origin
Where “atrial fibrillation” comes from
Atrial comes from the Latin atrium, the entrance hall of a house, borrowed for the receiving chambers of the heart. Fibrillation comes from fibrilla, a small fiber.