Assessment of the anatomical variation to be found in the normal tricuspid valve.

The normal tricuspid valve is tri-leaflet, supported by tendinous cords, which are themselves supported by papillary muscles. There can be marked variation in the anatomy of the normal tricuspid valve, which must be understood to differentiate it from pathological malformations. The tricuspid valve of 100 normal heart specimens was examined. The three leaflets of the tricuspid valve, along with the papillary muscles supporting the zones of apposition were identified, and details of the anatomy recorded and analyzed. All three leaflets were identified in all 100 hearts. The septal leaflet had tendinous cord attachments in 93 specimens to the ventricular septum. The medial papillary muscle had a single head in the majority of specimens, supporting the zone of apposition with the antero-superior leaflet in 97 specimens. The anterior papillary muscle attached to the mid-portion of the antero-superior leaflet in 62 specimens, and supplied the zone of apposition between the antero-superior and inferior leaflets in 81 specimens. There were rough zone cord attachments to the antero-superior leaflets in all specimens. The inferior leaflet had basal cord attachments in 87 specimens, with attachments to multiple small muscular heads in 37 specimens. The inferior papillary muscle was well formed in only 58 specimens. Although certain features are relatively constant, multiple variations in the normal tricuspid valve have been identified. Knowledge of these normal variations is necessary in understanding the function of this complex valve apparatus, along with the potential for pathology.