Atrial flutter

Definition

Atrial flutter is a rapid, regular atrial rhythm caused by an atrial macroreentrant circuit; the atria depolarize at 250–350/min (typically about 300/min).

• Typical atrial flutter: reentry around the tricuspid valve in the right atrium that necessarily conducts through the cavotricuspid isthmus (between the orifice of the inferior vena cava and the tricuspid annulus)
• Counterclockwise (most common form): negative sawtooth flutter waves in II, III and aVF, positive in V1
• Clockwise (less common, "reverse typical"): inverted pattern with positive flutter waves in II, III and aVF and negative in V1; also isthmus-dependent
• Atypical atrial flutter: macroreentry not involving the cavotricuspid isthmus, in the right or left atrium, often around scar tissue or fibrotic areas in the atrium

Classification

AV conduction

• 2:1 conduction (most common): atrial rate typically 300/min, regular ventricular rate of 150/min
• Variable conduction: irregular ventricular rhythm
• Fixed 3:1, 4:1 or 5:1 conduction: less common, with a correspondingly slower ventricular rate
• 1:1 conduction: rare, with a very high ventricular rate and hemodynamic compromise

Occurrence & epidemiology

Atrial flutter is much less common than atrial fibrillation but has similar causes and hemodynamic consequences. The two arrhythmias often coexist: in a population-based study, 69 % of people with newly diagnosed atrial flutter were already known to have atrial fibrillation, and 40 % of the others developed atrial fibrillation within three years.

Aetiopathogenesis

The causes largely correspond to those of atrial fibrillation: arterial hypertension, coronary artery disease, cardiomyopathies, valvular heart disease, hyperthyroidism, binge drinking, pulmonary embolism, COPD and congenital heart defects. The atria depolarize at 250–350/min; the AV node usually cannot conduct this rate completely and acts as a filter.

Clinical features

• Symptoms depend mainly on the ventricular rate and any underlying heart disease; with a regular rate below 120/min there are often few or no symptoms.
• Faster rates and variable conduction cause palpitations; reduced cardiac output leads to chest discomfort, dyspnea, weakness or syncope.
• Flutter a waves are visible in the jugular venous pulse.
• Atrial thrombi may form and embolize; the risk in isolated atrial flutter is estimated at about half that in atrial fibrillation.

Diagnosis

• The diagnosis is made by ECG: continuous, regular atrial activation with a sawtooth pattern, most obvious in leads II, III and aVF.
• A regular narrow-complex tachycardia at about 150/min suggests atrial flutter with 2:1 conduction, because flutter waves are then partly hidden in the QRS complex or T wave.
• Carotid sinus massage can transiently increase AV block and expose the flutter waves more clearly.
• In addition: echocardiography (structural heart disease, thrombi), thyroid function tests, ambulatory ECG; electrophysiological study clarifies the mechanism in atypical flutter.

Keep learning in the app

Further reading (open access)

1. MSD Manual Professional: Atrial Flutter
2. StatPearls: Atrial Flutter
3. Cavotricuspid Isthmus-Dependent Atrial Flutter (Rev Cardiovasc Med 2024, PMC11262378)

Cross-references