Coaptation Triangle and Golden Proportion in mitral valve anatomy. Does nature play with geometry?

The Coaptation Triangle, or Tenting Area, can be identified on long-axis 2D images. Its assessment is a routine practice during echocardiographic mitral evaluation. The Golden Proportion is a particular geometric ratio between two segments. Its value is an irrational number, commonly rounded to 0.618 and showing unique geometrical/mathematical properties. Interestingly, its presence has been documented in an extremely variable number of natural settings. Hypothesizing the presence of the Golden Proportion in normal mitral anatomy, we examined the Coaptation Triangle of healthy valves to investigate such a theory.

A total of 41 healthy adults, with normal mitral valves, underwent 2D echocardiography. Adequate images were chosen and loaded into custom software. Firstly, the Coaptation Triangle was manually drawn by the operator. Then, a second Coaptation Triangle, with the same base, but based on Golden Proportion, was automatically built by the software. Eventually, the two triangles were analyzed and compared. All retrieved measurements were investigated for differences and correlations. Ratios close to the Golden Proportion were found in several locations of the manually drawn Coaptation Triangle. On the other hand, comparing the manually drawn Coaptation Triangle with the automatically built one, no significant differences were revealed, and very strong correlations were demonstrated.

The Golden Proportion appears present in the geometry of normal mitral valves. Studying such an aspect and identifying disruption in anatomical proportions could improve early diagnosis of mitral alterations, and allows a more standardized follow-up and help surgeons to plan a repair strategy, particularly quantifying the needed surgical modifications.