Steps, arches, and struts supporting the aortic leaflet of the mitral valve

The study aim was to re-examine the form and function of the cords exclusive to the aortic leaflet of the mitral valve.

The ventricular surface of the leaflet was exposed by a longitudinal incision between the coronary sinuses of the aorta. The cords exclusive to the leaflet, in between the so-called commissural cords on either side shared with the mural leaflet, were inspected visually in 75 human hearts obtained at autopsy.

The cords were found to form two groups: (i) cords to the free edge, which support the gossamerthin free edge of the leaflet, and provide a low-pressure, bloodtight seal; and (ii) belly cords, which insert into the ventricular surface of the leaflet, usually forming graceful steps and arches between the lateral and medial groups of cordal support. Among these belly cords were found strut cords, which course perpendicular to the steps and arches.

The so-called cords to the rough zone, better considered as belly cords, must be distinguished from cords supporting the free edge of the leaflet, as they have different forms and subserve a different function. The belly cords usually form steps, arches and struts, which facilitate the distribution of stress, whereas the cords supporting the free edge function to provide a blood-tight seal. An understanding of the pattern and variations in cordal support is necessary to appreciate the pathology, and to tailor restoration in the surgical repair of diseased valves.