Atrial flutter is similar to atrial fibrillation in many ways but is less common. The two arrhythmias often occur together in the same patient and may be indistinguishable by ECG. In atrial flutter, unlike atrial fibrillation, the atrial rate tends to be regular at 250-350 beats per minute. Like atrial fibrillation, there is virtually always some degree of AV block, usually in a 2:1 pattern, such that the ventricular rate is usually around 150 beats per minute; in fact, atrial flutter can be confused with sinus tachycardia at 150 beats per minute. Under certain circumstances the AV node transmission can be unstable or erratic, which may result in a very irregular heartbeat simulating that of atrial fibrillation.
The incidence of atrial flutter is unclear. It occurs at any age including infancy and appears to be more common in males than in females. Atrial flutter often occurs in the first week after open-heart surgery in both children and adults and frequently follows surgery to repair congenital heart defects over both short and long term. In clinical practice it is usually associated with underlying heart disease, chronic obstructive pulmonary disease, mitral or tricuspid valve disease, and hyperthyroidism.
Atrial flutter is subdivided into two types. Typical atrial flutter has a very characteristic ECG pattern and is caused by localized reentry with impulse pathways occupying large portions of the right atrial wall. Since the circuit is fixed and accessible, typical atrial flutter can often be cured by destroying a portion of the circuit during a special procedure known as ablation. Atypical atrial flutter, on the other hand, exhibits a more variable ECG pattern, and more than one circuit may be responsible. Atypical atrial flutter behaves much more like atrial fibrillation than does typical atrial flutter.
Therapy of atrial flutter is similar to that for atrial fibrillation. DC cardioversion to convert atrial flutter to sinus rhythm has a high likelihood of success. Intraatrial pacing has also been used to terminate atrial flutter with good results. In some patients, medications can effectively terminate atrial flutter and prevent its recurrence; in those patients in whom the circuit cannot be ablated, medications may be necessary for prevention of recurrences. If sinus rhythm cannot be maintained by either ablation or medication, ventricular rate control may be necessary using either medications or AV nodal ablation and ventricular pacing. Since atrial flutter and fibrillation frequently coexist, the risk of embolic stroke is may be increased. Anticoagulation to decrease stroke risk should therefore be considered as part of all therapies for atrial flutter.