Atrial fibrillation is characterized by all of the following EXCEPT:

Atrial fibrillation is characterized by all of the following EXCEPT:

• A. An atrial rate of 120-200 beats/min and a ventricular rate of 300-600 beats/min
• B. Normal shape and duration of the QRS complex
• C. The presence of fibrillatory (F) waves instead of P waves
• D. A highly variable P:QRS ratio

Answer: (A)

Recognize the ECG pattern of atrial fibrillation: there are chaotic atrial impulses with no discrete P waves, replaced by fibrillatory waves, and the ventricular rhythm is irregularly irregular with varying R–R intervals. The QRS complexes are typically normal in shape and duration unless there’s a conduction abnormality. Atrial fibrillation usually features a very fast atrial rate, roughly 350–600 beats per minute, while the ventricular rate is variable and not in the extremely high range of 300–600; it often falls around 100–180 bpm with rapid ventricular response. So the statement describing atrial rate of 120–200 and ventricular rate of 300–600 does not fit atrial fibrillation. The other characteristics—normal QRS shape, fibrillatory waves instead of P waves, and a highly variable P:QRS ratio—are consistent with AF.

Recognize the ECG pattern of atrial fibrillation: there are chaotic atrial impulses with no discrete P waves, replaced by fibrillatory waves, and the ventricular rhythm is irregularly irregular with varying R–R intervals. The QRS complexes are typically normal in shape and duration unless there’s a conduction abnormality. Atrial fibrillation usually features a very fast atrial rate, roughly 350–600 beats per minute, while the ventricular rate is variable and not in the extremely high range of 300–600; it often falls around 100–180 bpm with rapid ventricular response. So the statement describing atrial rate of 120–200 and ventricular rate of 300–600 does not fit atrial fibrillation. The other characteristics—normal QRS shape, fibrillatory waves instead of P waves, and a highly variable P:QRS ratio—are consistent with AF.