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Ann Thorac Surg 1995;59:427
© 1995 The Society of Thoracic Surgeons

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Invited Commentary

Invited Commentary

Heineman Medical Research Laboratory Carolinas Medical Center Charlotte, NC 28203

See also page 419.

This article by Sutton and colleagues emphasizes the importance of interleaflet triangles in understanding the surgical anatomy of the aortic valve and reminds us that the prosthetic valves are sewn partly to this structure. They also support a view that the aortic root anatomy should be described with regard to structure and function. I would like to carry this further and state that the function should include fluid dynamics as well as the mechanical stresses in the valve.

Interleaflet triangles are subjected to ventricular systolic pressures that induce complex patterns of significantly high wall stresses. In a transverse plane, the triangles do not form a circular ring; instead, they form short lines that connect a cloverleaf geometry of the sinuses. This complex geometry induces bending stresses that increase distally in the triangle. Although thin, the tissue in the interleaflet triangle, therefore, must be strong enough to sustain the imposed stresses, which enables it also to support a prosthetic valve. On the other hand, the interfeaflet triangles do not ``support'' the leaflets (ie, the leaflets do not pull on the triangles), whereas the stent posts of bioprosthetic valves do, which may therefore cause bending of the stent posts inward from the pressure load on the valve. The leaflet of the aortic valve forms a unique structure in conjunction with the sinus, which could be called ``leaflet–sinus assembly'' [1]. This leaflet–sinus assembly behaves as an independent unit to store the diastolic pressure within. When the aorta is separated from the heart, the assembly allows the aortic valve to remain competent even if the interleaflet triangles are partly incised. This assembly gives a unique feature to the sinus geometry, in that, a sinutubular ridge forms a scalloped structure. Thus, the sinutubular junction is not circular as claimed by Sutton and associates.

The concept of a suspension bridge, put forth by Sutton and associates, also should be reconsidered in the light of the previous discussion. Certainly the studies on the dynamics of the interleaflet triangle are important not only for understanding the aortic root, but also for evaluating how well it supports a prosthetic valve. Sutton and associates deserve credit for studying the interleaflet triangles.

Reference

1. Thubrikar MJ. The aortic valve. Boca Raton, FL: CRC Press, 1989:119–26.

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