Which dysrhythmia results from the continuous stimulation of two conduction pathways in the atrioventricular node?

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

Answer: (C)

Atrial fibrillation is defined by continuous, disorganized atrial activity driven by multiple ectopic foci and micro-reentrant circuits. This relentless atrial bombardment sends a flood of impulses to the AV node, which can only conduct some of them to the ventricles in an irregular, unpredictable pattern. The result is an irregularly irregular heart rhythm with no discrete P waves on the ECG and an unpredictable, often rapid ventricular response.

This contrasts with atrial flutter, which typically shows a regular sawtooth atrial pattern; sinus tachycardia, which is a normal-appearing rhythm with a uniformly faster rate and identifiable P waves; and ventricular tachycardia, which originates in the ventricles and usually presents with wide QRS complexes and a fast rate. The chaotic atrial activity and irregular conduction to the ventricles make atrial fibrillation the best fit for a rhythm arising from continuous, noncoordinated atrial impulses that overwhelm the conduction pathway through the AV node.