What is the term for rapid, uncoordinated contractions of heart muscle fibers that affect the heart’s ability to pump blood?

The correct term for rapid, uncoordinated contractions of heart muscle fibers that impair the heart's ability to pump blood is fibrillation. This condition can occur in both the atria and ventricles, leading to inefficient blood circulation.

When fibrillation occurs, the electrical signals in the heart can become chaotic, resulting in the heart muscles quivering rather than contracting in a coordinated manner. This disorganization prevents effective blood pumping, which can be life-threatening if not treated promptly. In cases of ventricular fibrillation, for example, blood is not effectively pumped to the organs, leading to sudden cardiac arrest.

In contrast, other options represent different types of arrhythmias or cardiac conditions. Ventricular tachycardia, for instance, refers to a rapid but organized heartbeat originating from the ventricles, which can still support some level of blood flow. Atrial flutter involves a rapid and organized rhythm in the atria, while heart block denotes a delay or complete block in the electrical signals traveling through the heart tissues, affecting the heart’s rhythm but not causing the chaotic contractions seen in fibrillation.