How would you recognize atrial fibrillation on an EKG?

• A. An irregularly irregular rhythm with absent distinct P waves and variable R-R intervals; risk of embolic stroke; management depends on rate control or rhythm control and anticoagulation.
• B. A regular rhythm with distinct P waves.
• C. A flatline on the tracing.
• D. A rapid rhythm with a consistent R-R interval.

Answer: (A)

On an ECG, atrial fibrillation is identified by an irregularly irregular rhythm with no distinct P waves. The atria are beating chaotically, so there is no coordinated atrial contraction and the impulses reaching the ventricles come through the AV node in an unpredictable, variable fashion. This produces a baseline that looks erratic or fibrillatory, and the intervals between QRS complexes vary from beat to beat.

This pattern stands in contrast to normal sinus rhythm, where P waves precede every QRS and the R-R intervals are regular; a flatline indicates no electrical activity at all; and a rapid rhythm with a consistent R-R interval suggests another tachycardia with regular conduction, not AF. Recognizing this irregular, P-wave–less pattern is important because atrial fibrillation increases the risk of embolic stroke and often requires decisions about rate control or rhythm control and anticoagulation based on stroke risk.