Cardiovascular

Atrial Flutter

Atrial flutter is a single organised re-entry circuit, usually running around the tricuspid valve, and the ventricular rate is whatever fraction of it the atrioventricular node lets through.

Definition

An organised macro-re-entrant atrial tachycardia. Typical flutter is cavotricuspid-isthmus dependent and circles the tricuspid annulus, running counter-clockwise (common) or clockwise (reverse). Atypical flutter uses another circuit, usually related to atrial scar.

First principles

One circuit, one isthmus, and that is why flutter can be cured

Typical flutter is a large right-atrial circuit around the tricuspid annulus, and every lap passes through a narrow corridor called the cavotricuspid isthmus. The circuit is anatomically fixed, so a single ablation line across that isthmus breaks it. Atypical flutter uses a different circuit, usually around scar after cardiac surgery or a previous ablation, and needs specialist mapping instead. This is the structural difference from atrial fibrillation, which has no single target to ablate.

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