Atrial flutter (AFL) is a rapid arrhythmia that falls between atrial tachycardia and atrial fibrillation. It is rare in healthy individuals and often associated with structural heart disease.
Etiology
Atrial flutter is commonly seen in patients with coronary artery disease, valvular disease, hypertensive heart disease, and cardiomyopathy. Other causes include pulmonary embolism, hyperthyroidism, alcohol intoxication, and pericarditis. Some patients may have no obvious cause.
Clinical manifestations
Symptoms are mainly related to the ventricular rate. When the ventricular rate is not fast, patients may be asymptomatic. Atrial flutter with a very rapid ventricular rate can trigger angina and heart failure. Atrial flutter has an unstable tendency, potentially reverting to sinus rhythm or progressing to atrial fibrillation, but it can also persist for months or years. Patients may develop atrial thrombi, leading to thromboembolism. Physical examination may reveal rapid jugular venous pulsations. The intensity of the first heart sound changes with variations in AV conduction ratio, and atrial sounds may sometimes be heard.
Electrocardiogram features
ECG features include:
- Sinus P waves are absent and replaced by regular, sawtooth flutter waves called F waves, with no isoelectric line between them, typically at a rate of 250 - 350 bpm
- The ventricular rate may be regular or irregular, depending on the constancy of the AV conduction ratio, often alternating between 2:1 and 4:1 conduction
- The QRS morphology is usually normal, but may be widened and abnormal with intraventricular aberrant conduction, preexisting bundle branch block, or conduction through an accessory pathway
Figure 1 Atrial flutter
In leads II and V1, rapid and regular sawtooth F waves are visible at a rate of 300 bpm, with a regular RR interval and a 3:1 AV conduction ratio.
Treatment
Medication treatment
Drugs to slow the ventricular rate include β-blockers, non-dihydropyridine calcium channel blockers (verapamil, diltiazem), or digitalis glycosides (digoxin, lanatoside C). Drugs to convert atrial flutter and prevent recurrence mainly include class III antiarrhythmics (ibutilide, dofetilide, and amiodarone). Ibutilide is used for recent-onset atrial flutter but is contraindicated in severe structural heart disease, prolonged QT interval, and sinus node dysfunction. Dofetilide is another option. For long-term maintenance of sinus rhythm, amiodarone, dofetilide, or sotalol may be used.
Non-medication treatment
In hemodynamically unstable acute patients, immediate synchronized direct current cardioversion is performed. Symptomatic, recurrent, or persistent atrial flutter causing tachycardia-induced cardiomyopathy should be treated with catheter ablation.
Anticoagulation therapy
Patients with persistent atrial flutter have a significantly increased risk of thromboembolism and should receive anticoagulation therapy, following similar strategies as for atrial fibrillation.