A 46-year-old man with a 3 year history of coronary artery disease is seen in the cardiac clinic for a follow-up visit:   

• Coarse atrial fibrillation, 86/min
• Inferior infarction, age undetermined

Coarse atrial fibrillation with fibrillatory waves seen during the entire 10 sec of recording is often misdiagnosed as atrial flutter.

Features that favour the diagnosis of atrial fibrillation are:

• Variations in the morphology and rate of the atrial waves (this is particularly evident in this case in lead II)
• Irregularly irregular QRS rhythm
• In coarse atrial fibrillation the flutter-like waves are more frequently seen in V1 (while the saw-toothed waves of flutter are more frequently seen in the inferior leads II, III and aVF)