 Aortic valve commissure

An aortic valve commissure is a region where adjacent aortic valve leaflets meet at their high peripheral attachment to the aortic root. In the usual three-leaflet valve, three commissures rise toward the sinotubular junction. They are high points of the crown-shaped attachment, distinct from the low landmarks defining the virtual basal ring.^[ref]

A commissural attachment should also be distinguished from coaptation. The commissure identifies a peripheral supporting location; coaptation describes apposition of mobile leaflet surfaces during closure. Knowing three attachment positions does not establish the entire contact area or exclude an intervening gap.

An original geometric model illustrates why the spatial arrangement matters. Put three attachment points on a circle of radius $R$ with equal angular spacing. The distance between neighbors isFor $R=15$ mm, $d\simeq 25.98$ mm. Keeping the same radius but moving two adjacent points to $90^{\circ }$ separation changes their distance to $2R\sin 45^{\circ }\simeq 21.21$ mm. A fixed circular diameter alone therefore does not determine every span between attachment sites.

Real aortic valve geometry includes leaflet shape, attachment height and deformation, not just points on a flat circle. The calculation explains which information is lost by replacing a spatial arrangement with one diameter; it does not provide a surgical target. Locating each aortic valve commissure helps make anatomical descriptions and imaging views comparable without identifying the whole valve with a single ring.