fibrillation

Imagine a hummingbird's wings: they do not move in slow, smooth strokes, but in very fast flutters. That gives you a rough picture of what happens here. It describes rapid, uncoordinated quivering of muscle fibers, especially in the heart. You will most often hear about atrial fibrillation, a common heart condition in which the upper chambers of the heart quiver instead of pumping in a steady way. This can be serious.

Think of a guitar string vibrating cleanly versus one shaking in a random way. This word is like that random shaking, breaking the normal rhythm. People often use it when talking about a fluttering feeling in the chest.

Fibrillation refers to an irregular, uncoordinated contraction of muscle fibers—think of it as a chaotic quivering instead of a strong, rhythmic beat. The word comes from the Latin fibrilla, meaning "small fiber," hinting at the tiny muscle movements involved. While it can occur in various tissues throughout the body, it is most often associated with the heart.

Atrial fibrillation (AFib) is a common type where the upper chambers of the heart (the atria) beat rapidly and irregularly, disrupting blood flow. While this isn't usually immediately life-threatening, it significantly increases the risk of stroke and other heart-related complications. Doctors might describe it as an "irregularly irregular" rhythm when listening to a patient's heartbeat.

However, fibrillation isn't only about the heart. Skeletal muscle fibers can fibrillate due to injury or nerve damage. For example, when a nerve is severed, the associated muscle fibers may begin to fibrillate as they lose their regulatory signals. While these tiny contractions are often invisible to the naked eye, they are a key diagnostic sign in medical testing.

The term can even be used metaphorically. You might say someone's voice was filled with "emotional fibrillation," meaning it trembled or wavered with intense feeling. But in medical contexts, it always refers to that rapid, uncoordinated quivering of muscle tissue. Whether describing a heart condition, nerve damage, or a metaphorical tremor, fibrillation signifies an erratic and disruptive lack of coordinated movement.