Atrial flutter and atrial tachycardia are arrhythmias confined to the atria and characterized by extremely rapid rates, over 220 beats per minute and typically 300 beats per minute. These rhythms often are regular and usually are produced either by a continuously reactivating reentrant electrical circuit or by repetitively activating areas that initiate electrial waves at rapid rates.

During atrial flutter or atrial tachycardia, the ventricles do not beat as rapidly as the atria because the conduction delay between the atria and ventricles prevents many atrial bioelectrical waves from reaching the ventricles. Despite compromised atrial contraction, this type of arrhythmia usually is not immediately life-threatening. However, it can lead to other heart problems if not treated.