What is the term for very rapid irregular contractions of the muscle fibers of the heart?

Fibrillation refers to the very rapid and irregular contractions of the muscle fibers of the heart, specifically the atria or ventricles. During fibrillation, instead of an organized contraction, the heart muscle quivers ineffectively, which can severely impair the heart's ability to pump blood and can lead to sudden cardiac arrest if not treated promptly. This condition is characterized by a chaotic electrical activity in the heart, resulting in disorganized contractions that do not propel blood effectively.

Understanding the context of the other terms can further clarify why fibrillation is the specific term in this case. Arrhythmia is a broader term that encompasses any irregularity in the heart's rhythm, which can include various abnormalities, but it does not specifically indicate the rapid and chaotic nature of fibrillation. Tachycardia refers to an increased heart rate, which can occur with a regular rhythm or in conjunction with fibrillation, but it does not define the irregular contractions themselves. Bradycardia, on the other hand, describes a slower than normal heart rate, which is opposite in nature to fibrillation.

In summary, fibrillation specifically captures the critical aspect of rapid and irregular contractions of the heart, distinguishing it from other heart rhythm disorders.