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Atrial flutter is a rapid regular atrial rhythm due to an atrial macro-reentrant circuit. Symptoms are mainly palpitations. Atrial thrombi may form and embolize. Diagnosis is by ECG. Treatment involves rate control with drugs, prevention of thromboembolism with anticoagulants, and often conversion to sinus rhythm with drugs or cardioversion.
Atrial flutter is much less common than atrial fibrillation, but its causes and hemodynamic consequences are similar. Many patients with atrial flutter also have periods of atrial fibrillation.
Classical atrial flutter is due to a large reentrant circuit involving most of the right atrium. The atria depolarize at a rate of 250 to 350/min (typically 300/min). Because the atrioventricular (AV) node cannot usually conduct at this rate, typically half of the impulses get through (2:1 block), resulting in a regular ventricular rate of 150 beats/min. Sometimes the block varies from moment to moment, causing an irregular ventricular rhythm. Less commonly, a fixed 3:1, 4:1, or 5:1 block may be present.
The probability of a thromboembolic event, once considered rare in atrial flutter, is now thought to be about half of that in atrial fibrillation.
Symptoms and Signs
Symptoms depend primarily on ventricular rate and the nature of any underlying heart disorder. If ventricular rate is < 120 beats/min and regular, there are likely to be few or no symptoms. Faster rates and variable AV conduction usually cause palpitations, and decreased cardiac output may cause symptoms of hemodynamic compromise (eg, chest discomfort, dyspnea, weakness, syncope). Close inspection of the jugular venous pulse reveals flutter a waves.
Diagnosis
The diagnosis is by ECG, which shows continuous and regular atrial activation with a sawtooth pattern, most obvious in leads II, III, and aVF (see Fig. 11: Arrhythmias and Conduction Disorders: Atrial flutter with variable atrioventricular block. ).
Carotid sinus massage can increase AV block and better expose the typical flutter waves. A similar response may follow pharmacologic AV nodal blockade (eg, with adenosine), but such therapy does not terminate atrial flutter.
Treatment
As for atrial fibrillation, treatment focuses on ventricular rate control, rhythm control, and prevention of thromboembolism. However, pharmacologic rate control is more difficult to achieve in atrial flutter than in atrial fibrillation. Thus for most patients, electrical conversion (using synchronized cardioversion or overdrive pacing) is the treatment of choice for an initial episode and is mandatory with 1:1 AV conduction or hemodynamic compromise. Typically, low-energy (50 joules) conversion is effective. Anticoagulation, as in atrial fibrillation, is necessary before cardioversion.
If drugs are used to restore sinus rhythm, rate must first be controlled with β-blockers or nondihydropyridine Ca channel blockers (eg, verapamil, diltiazem). Many of the antiarrhythmics that can restore sinus rhythm (especially class Ia and Ic) can slow atrial flutter, shorten AV nodal refractoriness (by their vagolytic effects), or do both enough to allow 1:1 conduction with paradoxical increase in ventricular rate and hemodynamic compromise. These drugs may be used for long-term maintenance as required to prevent recurrence.
An antitachycardia pacing system is an alternative to long-term use of antiarrhythmics in selected patients. Also, ablation procedures designed to interrupt the atrial reentrant circuit may effectively prevent atrial flutter, particularly classic atrial flutter.
Patients with chronic or recurrent atrial flutter require warfarin (to maintain an INR of 2 to 3) or aspirin therapy long-term. The choice between the 2 therapies is based on the same considerations as for atrial fibrillation.
Last full review/revision January 2008 by L. Brent Mitchell, MD
Content last modified January 2010
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