What is the life-threatening condition called when heart muscle fibers contract irregularly?

• A. Fibrillation
• B. Cardiac arrest
• C. Myocardial infarction
• D. Tachycardia

Answer: (A)

When heart muscle fibers contract irregularly, the electrical signals are chaotic and the heart quivers instead of pumping in a coordinated way. This irregular, uncoordinated activity is called fibrillation. It’s especially dangerous in the ventricles (ventricular fibrillation) because blood flow stops, leading to sudden cardiac death if not treated immediately with defibrillation and CPR. Tachycardia is a rapid but usually regular rhythm, myocardial infarction is a heart attack from blocked blood flow, and cardiac arrest is the abrupt stop of effective beating—conditions that can relate to fibrillation but aren’t the irregular contraction itself. The key idea is the disorganized, erratic firing that prevents the heart from pumping effectively.