Electrocardiogram in atypical atrial flutter

There are three findings that distinguish this arrhythmia from typical atrial flutter: the flutter rate is faster at 375 beats/minute; there is no isoelectric interval between the flutter waves; and there is more apparent positivity in leads II, III, and avF. The high degree of AV block is due to digoxin and some underlying AV nodal disease.

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.