Atypical atrial flutter

Atypical atrial flutter

Atypical atrial flutter with 2:1 conduction
Atypical atrial flutter with 2:1 conduction

Flutter waves are seen well in leads I, aVL, aVR and V1. In inferior leads the flutter waves appear more like usual P waves. This is unusual because in typical flutter the flutter waves are seen well in inferior leads (compare with the next image). Flutter waves are saw toothed in appearance and have a rate of 250 – 350 per minute. The ventricular rate may vary depending on the conduction ratio. One of the typical rates is 150/minute with atrial rate of 300 per minute and 2:1 conduction. In fact when the ventricular rate is 150/minute, one is supposed to look carefully for flutter waves in the ECG.

Typical atrial flutter has positive waves in V1 and negative waves in V6, II, III and aVF. The reentrant circuit is counterclockwise, ascending up along the interatrial septum and descending down along the right atrial free wall. The reverse pattern is seen in reverse typical atrial flutter. In reverse typical atrial flutter, the waves are negative in V1 and positive in V6, II, III and aVF. The reentrant circuit is clockwise, ascending up along the right atrial free wall and descending down the interatrial septum.

Typical atrial flutter with 4:1 conduction
Typical atrial flutter with 4:1 conduction

Atrial flutter is due a macro reentrant circuit, usually in the right atrium. Often, the zone of slow conduction is in the region of the cavotricuspid isthmus. As it is a macro reentrant arrhythmia it is one of the most sensitive ones to electrical cardioversion. Radiofrequency catheter ablation in the region of cavotricuspid zone of slow conduction can abolish the flutter circuit and prevent recurrence.