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Crista terminalis

The crista terminalis is a smooth, muscular ridge located along the posterior wall of the right atrium, extending from the superior vena cava (SVC) orifice to the inferior vena cava (IVC) orifice. It marks the junction between the sinus venarum (smooth posterior atrium derived from sinus venosus) and the anterior right atrial wall with pectinate muscles.

Embryologically, it represents the line of fusion of the right venous valve of the sinus venosus with the developing atrium. On the external surface, the sulcus terminalis corresponds to the crista terminalis.

Clinically, the crista terminalis is significant because it can be mistaken for a right atrial mass or thrombus on imaging, especially if prominent. It is also an electrophysiological landmark, often associated with atrial tachycardia foci.

Synonyms

  • Terminal crest

  • Crista terminalis atrii dextri

  • Right atrial ridge

Function

  • Serves as an anatomical landmark separating the smooth sinus venarum from pectinate muscles

  • Plays a role in right atrial conduction; may harbor ectopic foci in atrial arrhythmias

  • Acts as a radiologic and surgical landmark in the right atrium

MRI Appearance

T1-weighted images:

  • Appears as a low-to-intermediate signal muscular ridge along the lateral right atrial wall, best seen near the SVC–RA junction

T2-weighted images:

  • Seen as a low-signal linear structure against the bright blood pool of the right atrium

  • Distinguishable from thrombus or tumor by its smooth contour and typical location

T2 TRUFISP (cardiac-gated):

  • Clearly depicts the crista terminalis as a smooth intracavitary ridge with bright surrounding blood

  • Cine sequences confirm non-mobile, fixed ridge, differentiating it from right atrial masses

STIR (Short Tau Inversion Recovery):

  • Not routinely used for normal anatomy, but surrounding edema (if inflamed or involved by pathology) appears hyperintense

T1 Post-Contrast (Gadolinium-enhanced MRI):

  • The ridge enhances similarly to normal myocardium, unlike thrombus (non-enhancing) or tumors (heterogeneous enhancement)

  • Late gadolinium enhancement absent in normal crista terminalis

MRI Non-Contrast 3D Cardiac-Gated Imaging:

  • Provides a 3D view of right atrial anatomy, showing the crista as a thin muscular ridge from SVC to IVC orifice

  • Essential for electrophysiological mapping and surgical planning

CT Appearance

CT Coronary Angiography (CCTA):

  • Crista terminalis appears as a smooth, linear muscular prominence within the right atrium

  • Seen best in axial and 3D reconstructions along the lateral RA wall between SVC and IVC

  • Differentiated from masses or thrombus by contour, continuity, and density equal to myocardium

  • Important in avoiding misdiagnosis of right atrial tumor or thrombus

CT image

Crista terminalis anatomy CT axial image -img-00000-00000

MRI image

Crista terminalis MRI IMAGE