Single-lead electrocardiogram (ECG) showing atrial fibrillation

Lead V1 showing coarse AF with moderate ventricular response. The two characteristic findings in AF are present: the very rapid atrial fibrillatory waves (f waves), which are variable in appearance; and the irregularly irregular ventricular response as the R-R interval between beats is unpredictable. Coarse AF may appear similar to atrial flutter. However, the variable height and duration of the f waves differentiate them from atrial flutter (F) waves, which are identical in appearance and occur at a constant rate of about 250 to 350 beats/min.

Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright.