Atrial fibrillation is characterized by which of the following?

• A. Rapid, random, ineffective contractions of the atrium
• B. Regular contractions of the atrium
• C. Blockage of a coronary artery
• D. Inflammation of the atrium

Answer: (A)

Atrial fibrillation involves disorganized electrical activity in the atria, so the atria quiver instead of contracting in a coordinated, squeeze-like fashion. This creates a very fast and irregular heart rhythm because the ventricles respond to random atrial impulses rather than a steady signal. The phrase “rapid, random, ineffective contractions of the atrium” directly describes this chaotic atrial activity and the loss of organized atrial contraction that defines AFib.

In AFib you’d also expect an irregularly irregular pulse and, on ECG, the absence of distinct P waves with irregular intervals between beats. The other descriptions point to different problems: regular atrial contractions aren’t AFib, a coronary artery blockage suggests a heart attack, and inflammation of the atrium refers to a different inflammatory condition.