Figure 6. Appearance of atrial flutter or fibrillation in surface ECG leads II and V1. A, Type I atrial flutter with fixed (4:1) AV conduction and regular RR intervals. B, Type I atrial flutter with variable (2:1, 3:1, 4:1) AV conduction and changing RR intervals. C, Type II atrial flutter with fixed (2:1) AV conduction and a ventricular rate of 181 beats/min. Note right bundle branch block pattern QRS aberration in lead V1 and flutter waves in lead II. D, Atrial fibrillation with no recurring pattern of AV conduction and irregular RR intervals. There are no discernible P waves. Paper speed = 25 mm/s; 1 mV = 1 cm.