Figure 4c. Normal cardiac chambers. (a) CT scan of the right cardiac chambers demonstrates a muscular structure (arrowheads) between the tricuspid valve (TV) and the pulmonary valve (PV). The right ventricle shows coarse trabeculae. (b) CT scan of the left cardiac chambers demonstrates fibrous continuity (arrowhead) between the mitral valve (MV) and the aortic valve (AV). The left ventricle shows fine trabeculae. (c) CT scan shows the atrial appendages with a characteristic appearance. The right atrial appendage (RAA) is triangular with a wide opening, whereas the left atrial appendage (LAA) is narrow and fingerlike. (d) CT scan shows the crista (sulcus) terminalis (arrowhead), an anatomic landmark between the right atrium proper and the right atrial appendage.