Cardiovascular: MI, Heart Failure, Arrhythmias · USMLE Step 1

A patient with atrial fibrillation presents with an irregularly irregular pulse. Which structure is most commonly the source of abnormal electrical activity?

  1. Atrioventricular node
  2. Pulmonary vein ostia
  3. Bundle of His
  4. Left atrial appendage
Show answer and explanation

Correct answer: Pulmonary vein ostia

Ectopic foci in the pulmonary vein ostia commonly initiate atrial fibrillation through aberrant electrical activity.

Difficulty: Medium Question 6 of 20

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