Atrial flutter is a regular, narrow-complex tachycardia seen on electrocardiogram (ECG). It is characterized by an atrial rate of 250-350 bpm, with a ventricular rate usually 2:1, 4:1, or 5:1. The flutter waves are usually best seen in leads II, III, and aVF and are characterized by a "sawtooth" pattern. The ventricular rate is usually between 150-250 bpm, depending on the relationship between the atrial and ventricular rate. Treatment includes electrical or chemical cardioversion, antiarrhythmic medications, and ablation. If untreated, atrial flutter can lead to serious complications, such as stroke.