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Frederick C. Cobey studies quantitative cardiac imaging, including three-dimensional assessment of how the mitral valve leaflets meet during closure. He is first author of a 2014 primary study using transesophageal echocardiography to measure the valve's coaptation area and relate it to functional mitral regurgitation.^[ref] The published name and affiliations establish this contribution without expanding the middle initial.

The study examined 25 patients with functional mitral regurgitation undergoing cardiac operations. It used intraoperative two- and three-dimensional echocardiography, followed by offline measurement of the end-systolic coaptation zone and valve area.^[ref] The three-dimensional observation addresses an extended surface, rather than assuming that a single two-dimensional slice captures its full geometry.

The mitral coaptation index divides the measured coaptation zone area $A_c$ by the measured valve area $A_v$:An original normalization example takes $A_c=0.60\mathrm{c}{\mathrm{m}}^2$. Valve areas of 6 and $10\mathrm{c}{\mathrm{m}}^2$ then give indices 0.10 and 0.06, respectively. Equal coaptation area need not imply an equal proportion of the valve area. These are stipulated illustrations, not individual patient measurements from the paper.

If every reconstructed length is multiplied by the same scale factor $k$, both areas multiply by $k^2$ and the index is unchanged. The ratio consequently removes that common scale dependence. It does not remove a segmentation error affecting only the coaptation zone, nor does it compensate for measuring a different cardiac phase.

The primary study found an association between the index and the severity of functional mitral regurgitation in its examined sample.^[ref] Cobey's documented work connects an anatomical contact surface to a quantitative imaging observable. Its interpretation still depends on acquisition, surface identification and the population studied.

The mitral coaptation index is a dimensionless normalization of the mitral valve's coaptation area. In the primary method of Frederick C. Cobey and colleagues, it is the three-dimensional end-systolic coaptation-zone area divided by the three-dimensional mitral-valve area used in that protocol:The denominator and surface-reconstruction convention are part of the definition.^[ref]

The study used intraoperative transesophageal echocardiography in 25 patients with functional mitral regurgitation, followed by offline analysis of the end-systolic geometry.^[ref] This supplies an experimental acquisition context for the ratio; it does not make every area called annular area interchangeable with the protocol's valve-area measurement.

An original normalization example uses $A_{\mathrm{coaptation}}=1.5$ cm${}^2$ and $A_{\mathrm{MV}}=10$ cm${}^2$, giving $I_c=0.15$. A second constructed valve with areas 3 and 20 cm${}^2$ has the same index despite twice the absolute contact area. Conversely, keeping contact area 1.5 cm${}^2$ while changing the denominator to 15 cm${}^2$ gives $I_c=0.10$. Absolute area and normalized coverage answer different questions.

Uniformly scaling every length by a positive factor $s$ multiplies both areas by $s^2$, leaving $I_c$ unchanged. Inconsistent surface conventions do not cancel: counting two apposed faces in the numerator while counting their interface once in another reconstruction can change the ratio without a biological change.

Finally, the index does not describe the connectivity of any remaining gaps. Two contact patches with equal coaptation area and equal denominator can have different shapes and positions, as illustrated under coaptation area. The mitral coaptation index is a geometric descriptor to interpret alongside the reconstructed valve and blood flow, rather than a complete description of valve sealing.