Cardiac anatomy from right to left

Crista terminalis

In the right atrium lies the crista terminalis, a muscular ridge that runs from the entrance of the superior- to that of the inferior vena cava.
This structure separates the smooth part of the right atrium - the sinus venosus - from the trabecularized right atrial appendage. On the images below it is visible as a smooth linear structure (blue arrows).
This is not always the case, however, it may simulate a mass.

 

Axial (left) and coronal (right) reconstructions showing the crista terminalis (blue arrows) and its location in the right atrium