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).
I48.92 – Unspecified atrial flutter
5370000 – Atrial Flutter
- Sinus tachycardia – Will have a normal P wave (absent flutter waves) before each QRS complex on the ECG; however, they can be difficult to see if the heart rate (HR) is very fast. The HR usually slows down slightly after carotid sinus massage, with no abrupt changes in the rate. Usually a precipitating cause for sinus tachycardia is present, such as anxiety, stress, exercise, or any other reason for catecholamine surge. S1 is constant, and a waves are normal on jugular venous pulse (JVP).
- Atrial fibrillation – No P waves on ECG, rhythm irregularly irregular. Precipitating cause such as stress, alcohol, or other stimulants (incidence of AFL is not increased with caffeine). Variable S1 and absent a waves on JVP.
- Premature atrial complexes – Premature P wave on the ECG, which is usually different in morphology from the normal sinus P wave. Precipitating factors mentioned above may be present.
- Atrial tachycardia – Atrial rate of, usually, 150-200 bpm, and the P wave morphology is different from the normal sinus P wave. Variable degree of AV block maybe present. Variable intensity of S1 and a waves on JVP.
- Ventricular tachycardia – Absent P waves with wide QRS complex with a ventricular rate of 100-250 bpm on ECG. Most common predisposing condition is ischemic heart disease. If sustained, is life-threatening.
- Pre-excitation arrhythmias – Occur because of an accessory conducting pathway that connects the atria to the ventricles and bypasses the AV node. The most common example is WPW syndrome. PR interval is usually short due to the presence of a delta wave, which is an initial slurred upslope of the QRS complex. ST-T wave changes opposite in direction from the wide QRS complex are also present.