Atrial Flutter

Supraventricular tachyarrhythmia caused by a macro-reentrant circuit within the atria.

Aetiology

• Associated with hypertension, ischaemic heart disease, cardiomyopathy and thyroxytosis
Typical (CTI-dependent) atrial flutter
• Reentrant circuit located in the right atrium
• Involves the cavotricuspid isthmus (CTI) between the tricuspid valve and inferior vena cava
• Most common form of AFL
Atypical (non-CTI-dependent) atrial flutter
• Reentrant circuits outside the CTI
• May arise in:
• Left atrium
• Right atrium outside the CTI
• Often associated with:
• Prior cardiac surgery
• Previous atrial ablation
• Structural heart disease

Pathophysiology

• Caused by stable macro-reentry around anatomical or functional barriers

• Typical AFL
• Circuit rotates around the tricuspid annulus
• CTI acts as a zone of slow conduction critical for sustaining reentry
• Direction may be:
• Counterclockwise (most common)
• Clockwise

• Atypical AFL
• Circuits depend on atrial scars or remodeled tissue
• Mechanisms are more heterogeneous and complex

• Atrial remodeling, fibrosis, and conduction anisotropy facilitate AFL maintenance

Clinical presentation

• Palpitations

• Dyspnea

• Fatigue

• Reduced exercise tolerance

• Presyncope or syncope

Investigations

ECG

• Regular atrial activity without an isoelectric baseline

• Classic “sawtooth” flutter waves, especially in:
• Inferior leads (II, III, aVF)

• Ventricular response often shows:
• 2:1 atrioventricular conduction (ventricular rate ≈150 bpm)

• Atypical AFL presents variable ECG morphologies

Management

• Management of a symptomatic acute paroxysm is by cardioversion (DCCV or pharmacological)

• Patients who have been in atrial flutter for more than 1–2 days should be anticoagulated for 3 weeks prior to cardioversion

• Treatment of choice for recurrent atrial flutter is catheter ablation; other options include AV nodal blocking agents e.g. β-blockers and class III anti-arrhythmics e.g. amiodarone

Complications

• Chronic atrial flutter usually progresses to atrial fibrillation