The exact incidence of AFL in the general population is unknown, but incidence increases with age. The condition is more prevalent in men than in women by a ratio of up to 2:1.
Most cases of AFL are associated with an underlying condition, many of which are also associated with atrial fibrillation, though the latter is more common. Cases of AFL without an identifiable predisposing factor ("lone atrial flutter") are far less common.
Common causes and predisposing conditions include:
- Atrial enlargement, from various causes
- Chronic ventricular failure
- Mitral or tricuspid valve regurgitation or stenosis
- Post-cardiac surgery
- Congenital heart disease
- Pre-excitation syndromes like Wolff-Parkinson-White syndrome (WPW)
- Toxins (eg, alcohol)
- Metabolic conditions (eg, thyrotoxicosis)
- Chronic pulmonary disease and pulmonary embolism
- Obstructive sleep apnea
- Type I (typical, common, or counterclockwise isthmus-dependent) – Characterized by a circuit from the high right atrium, down the lateral wall, crossing the isthmus between the orifice of inferior vena cava and the annulus of the tricuspid valve. Slow conduction through the isthmus causes an excitable gap that allows the flutter wave to repeatedly depolarize the atrium, propagating the arrhythmia. Less often, the isthmus-dependent pathway rotates in the opposite direction, which results in "atypical" or "clockwise" type I flutter.
- Type II – Not fully characterized and broadly defined as an atrial tachycardia with the characteristic continuous, undulating pattern on ECG that does not fit the typical clockwise or counterclockwise flutter pattern. It is less frequent and usually has a higher atrial rate (greater than 350 bpm).