Atypical Flutter is typically characterized by which activation pattern?

• A. Left or Right sides, mostly eccentric but can be concentric, usually related to scar.
• B. CTI-dependent concentric
• C. Right atrial appendage dependent
• D. AVN dependent

Answer: (D)

Atypical flutter is defined by macroreentrant circuits in the atria that do not rely on the CTI. Scar tissue from prior disease or ablation creates nonuniform conduction pathways, so the flutter circuit often travels around or through these scar areas rather than around the tricuspid annulus. This leads to an activation pattern that is predominantly eccentric—occurring in either the right or left atrium and not confined to a smooth, circular path around the CTI. While some atypical circuits can involve the RA appendage or other regions, the hallmark is scar-related, eccentric activation rather than a CTI-dependent, concentric pattern. In contrast, typical flutter is CTI-dependent with concentric activation around the tricuspid annulus.