Rapid regular sawtooth-like oscillations, best seen in leads II, III, aVF and V1 (flutter waves). The atrial rate is usually 240-340/min, although it may be slower following antiarrhythmic therapy. In the absence of therapy, the AV conduction is usually 2:1. With therapy or AV conduction abnormality, the conduction block may increase to 3:1, 4:1 or more, and may be variable. With 2:1 block, the flutter waves may be difficult to identify. Sometimes, if there are premature ventricular complexes, the flutter waves may be seen in “the window” following the PVC.
