Which of the following rhythms is characterized by irregular electrical activity of the heart?

• A. Ventricular fibrillation
• B. Atrial flutter
• C. Sinus tachycardia
• D. Normal sinus rhythm

Answer: (A)

Ventricular fibrillation is characterized by chaotic and irregular electrical activity in the heart, leading to ineffective contractions of the ventricles. This results in the heart being unable to pump blood effectively, which can quickly lead to loss of consciousness and is a life-threatening emergency. In this rhythm, the ventricular muscle fibers contract in a disorganized manner, preventing the heart from maintaining a normal rhythm and ultimately causing a state of cardiac arrest if not treated promptly.

In contrast, atrial flutter typically exhibits a more organized pattern of electrical activity that occurs in the atria, although it is still irregular compared to normal rhythms. Sinus tachycardia and normal sinus rhythm present with regular electrical activity, with sinus tachycardia simply indicating a faster rate of the regular sinus activity. Therefore, when assessing rhythm irregularity, ventricular fibrillation stands out as the clear answer due to its markedly disorganized electrical activity.