 Coaptation

Coaptation is the meeting and contact of opposing valve leaflet surfaces that helps a heart valve close. It is a geometrical and contact mechanics condition, distinct from the opening size, leaflet length or a single chordal tension measurement. The resulting contact region can be described by its location and coaptation area.

An original one-dimensional coverage model makes the role of support geometry clear. Let two opposing leaflets each reach a distance $\ell$ across an opening of width $D$. A nominal overlap margin isWith $\ell =16$ mm and $D=30$ mm, the margin is 2 mm. If the opening widens to 34 mm with unchanged reach, the margin becomes $-2$ mm, representing a gap in this simplified model. Actual leaflet contact also depends on three-dimensional orientation, deformation and loading, so positive overlap in a drawing is not sufficient proof of a seal.

A primary left-heart simulator study compared flat and saddle-shaped attachment boundaries in eleven human specimens of the mitral valve. Changes in cardiac valve annulus shape redistributed chordae tendineae forces; the tested shape comparison did not produce a statistically significant change in regurgitant volume.^[ref] Geometry, attachment forces and leakage were related but separately observed quantities.

This explains why a successful-looking contact region in one image need not specify the total backward blood flow. A narrow unobserved gap elsewhere may matter, while a contact outline supplies no direct measurement of its fluid transport. Conversely, measuring one chord's tension does not establish the contact state over every leaflet surface. A clear description of coaptation therefore identifies the valve, imaging phase and contact measure being discussed.