What is the condition called when heart cells quiver or spontaneously contort?

The condition where heart cells quiver or spontaneously contort is known as fibrillation. This is a serious cardiac arrhythmia characterized by the rapid and chaotic electrical activity in the heart, particularly affecting the heart's atria or ventricles. During fibrillation, the normal rhythm of the heart is disrupted, leading to ineffective contractions that fail to adequately pump blood throughout the body.

Fibrillation can result in severe complications, including reduced blood flow to vital organs, and if not treated promptly, may lead to cardiac arrest. The terminology is critical here; while flutter refers to a different type of rhythm disturbance that also involves the heart, fibrillation specifically describes the erratic electrical activity that results in quivering of the heart muscle.

In contrast, the other terms listed refer to different types of conditions or states: cramps typically refer to muscle spasms elsewhere in the body, tachycardia describes an abnormally fast heart rate, and flutter (like atrial flutter) is a more organized rhythm compared to fibrillation. Understanding these distinctions clarifies why the term fibrillation is the correct designation for the condition described in the question.