Atrial flutter is a form of supraventricular tachycardia characterised by a succession of rapid atrial depolarisation waves.

Pathophysiology

• a large, stable re-entry loop develops in the right atrium
• the circuit continuously re-excites atrial tissue
• it circles around the tricuspid annulus
• the cavotricuspid isthmus (between the tricuspid valve and IVC) is a critical slow-conduction zone
  • located between the tricuspid valve annulus and the inferior vena cava (IVC)
• because the circuit is anatomically fixed, the rhythm is highly regular
• this anatomical dependence explains why catheter ablation is very effective

ECG findings

• 'sawtooth' appearance
• as the underlying atrial rate is often around 300/min the ventricular or heart rate is dependent on the degree of AV block. For example if there is 2:1 block the ventricular rate will be 150/min
• flutter waves may be visible following carotid sinus massage or adenosine

Management

• is similar to that of atrial fibrillation although medication may be less effective
• atrial flutter is more sensitive to cardioversion however so lower energy levels may be used
• radiofrequency ablation of the cavotricuspid isthmus is curative for most patients
  • This region, located between the tricuspid valve annulus and inferior vena cava, represents a critical slow-conduction zone within the macroreentrant circuit. Ablation creates a line of conduction block across this isthmus, interrupting the circuit and achieving cure rates exceeding 90%.