Is the morphologically right atrioventricular valve tricuspid?

BACKGROUND AND AIM OF STUDY

Classification of the components of the right atrioventricular valve by its anatomical configuration is problematic and needs clarification.

METHODS

Fifty hearts were studied so as to analyze carefully the structure of the right atrioventricular valve and to define its component parts. Cross-sectional echocardiograms were reviewed to demonstrate the valve in closed position, and reconstructed in three-dimensional fashion.

RESULTS

The majority of specimens (62%) had three readily identifiable leaflets, but some (30%) could be described as having two leaflets while (8%) had four leaflets. The cross-sectional echocardiograms reviewed showed three definite lines of closure in all cases.

CONCLUSIONS

The eccentric placement of the anterior papillary muscle causes the leaflets to close with three lines of apposition, and this makes the valve readily distinguishable from its mitral partner. When present, extra "scallops" in the structure of the right atrioventricular valve merely allow better coaption of the leaflets. So, although the term "cusp" is less than adequate as the descriptive basis for the structure of an atrioventricular valve, the right atrioventricular valve should still be considered to be tricuspid.