Cavotricuspid isthmus
Isthmus cavotricuspidalis
- Synonym: Inferior isthmus of right atrium
Definition
The cavotricuspid isthmus is a region of the inferior right atrial wall, involved in the pathophysiology of atrial flutter. It is a roughly quadrilateral-shaped area bordered anteriorly by the tricuspid valve annulus, posteriorly by the Eustachian valve and ridge, superomedially by the inferior border of the coronary sinus ostium, and inferolaterally by the terminal crest (crista terminalis).
The isthmus is not flat; it often contains a sub-Eustachian pouch or recess, which may be deep or aneurysmal in some individuals.
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