Which mechanism best explains atrial fibrillation?

Study for the PANCE Cardiology Test. Enhance your knowledge with comprehensive flashcards and multiple-choice questions. Each question comes with hints and detailed explanations. Prepare thoroughly for your exam!

Multiple Choice

Which mechanism best explains atrial fibrillation?

Atrial fibrillation arises when the atria are bombarded with rapid, chaotic impulses that produce disorganized atrial depolarizations and ineffective atrial contraction. Often, ectopic atrial foci—frequently around the pulmonary veins—fire impulses at a high rate and serve as triggers. The ventricle then responds to these rapid impulses through the AV node, which cannot conduct every impulse due to its own refractory properties. This partial or variable AV nodal conduction creates an irregularly irregular ventricular rhythm, the hallmark of AF. So, when rapid ectopic atrial foci are firing and the AV node partially blocks or variably conducts those impulses, you get the disorganized atrial activity with an unpredictable, irregular ventricular response that defines atrial fibrillation. The other mechanisms describe different arrhythmias: a reentrant circuit within the AV node causes AVNRT; a ventricular ectopic focus causes ventricular tachycardia; AV node ablation is a treatment, not the mechanism.

Atrial fibrillation arises when the atria are bombarded with rapid, chaotic impulses that produce disorganized atrial depolarizations and ineffective atrial contraction. Often, ectopic atrial foci—frequently around the pulmonary veins—fire impulses at a high rate and serve as triggers. The ventricle then responds to these rapid impulses through the AV node, which cannot conduct every impulse due to its own refractory properties. This partial or variable AV nodal conduction creates an irregularly irregular ventricular rhythm, the hallmark of AF.

So, when rapid ectopic atrial foci are firing and the AV node partially blocks or variably conducts those impulses, you get the disorganized atrial activity with an unpredictable, irregular ventricular response that defines atrial fibrillation. The other mechanisms describe different arrhythmias: a reentrant circuit within the AV node causes AVNRT; a ventricular ectopic focus causes ventricular tachycardia; AV node ablation is a treatment, not the mechanism.

More practice questions