Atrial flutter (AFL) is an abnormal heart rhythm that occurs in the atria of the heart. When it first occurs, it is usually associated with a fast heart rate or tachycardia (beats over 100 per minute), and falls into the category of supra-ventricular tachycardias. While this rhythm occurs most often in individuals with cardiovascular disease (e.g. hypertension, coronary artery disease, and cardiomyopathy) and diabetes, it may occur spontaneously in people with otherwise normal hearts. It is typically not a stable rhythm, and frequently degenerates into atrial fibrillation (AF). However, it does rarely persist for months to years.

Atrial flutter was first identified as an independent medical condition in 1920 by the British physician Sir Thomas Lewis (1881–1945) and colleagues.

Signs and symptoms
While atrial flutter can sometimes go unnoticed, its onset is often marked by characteristic sensations of regular palpitations. Such sensations usually last until the episode resolves, or until the heart rate is controlled.

Atrial flutter is usually well tolerated initially (a high heart rate is for most people just a normal response to exercise), however, people with other underlying heart disease or poor exercise tolerance may rapidly develop symptoms, which can include shortness of breath, chest pains, lightheadedness or dizziness, nausea and, in some patients, nervousness and feelings of impending doom.

Prolonged fast flutter may lead to decompensation with loss of normal heart function (heart failure). This may manifest as effort intolerance (exertional breathlessness), nocturnal breathlessness, or swelling of the legs or abdomen.

Atrial flutter is recognized on an electrocardiogram by presence of characteristic flutter waves at a regular rate of 240 to 440 beats per minute. Individual flutter waves may be symmetrical, resembling p-waves, or may be asymmetrical with a "sawtooth" shape, rising gradually and falling abruptly or vice versa. If atrial flutter is suspected clinically but is not clearly evident on ECG, acquiring a Lewis lead ECG may be helpful in revealing flutter waves.

Management
In general, atrial flutter should be managed the same as atrial fibrillation. Because both rhythms can lead to the formation of thrombus in the atria, individuals with atrial flutter usually require some form of anticoagulation or anti-platelet agent. Both rhythms can be associated with dangerously fast heart rate and thus require medication for rate and or rhythm control. Additionally, there are some specific considerations particular to treatment of atrial flutter.

Cardioversion

Atrial flutter is considerably more sensitive to electrical direct-current cardioversion than atrial fibrillation, and usually requires a lower energy shock. 20-50J is commonly enough to revert to sinus rhythm. Conversely, it is relatively resistant to chemical cardioversion, and often deteriorates into atrial fibrillation prior to spontaneous return to sinus rhythm.

Ablation

Because of the reentrant nature of atrial flutter, it is often possible to ablate the circuit that causes atrial flutter. This is done in the electrophysiology lab by causing a ridge of scar tissue that crosses the path of the circuit that causes atrial flutter. Ablation of the isthmus, as discussed above, is a common treatment for typical atrial flutter.