Figure 2: Cross-profile shows how the idea emerged: a. Posterior annulus (5 or 7 o’clock position), p. Papillary muscle, e. Edge of anterior leaflet (5 or 7 o’clock position). The triangle a.p.e is an equilateral triangle. The plane of the posterior wall of left ventricle outflow tract extends from the tips of the papillary muscles to the anterior annulus of mitral valve. In the physiological condition this plane is curved slightly during the end diastole. The length of the first order native chord of the anterior leaflet “p-e” has approximately the same length of the first and second order of the posterior leaflet. Therefore, the distance between the posterior annulus and the tip of appropriate papillary muscle (not always the third order chord of posterior leaflet) is equal to the length of the first order chord of the anterior leaflet which is located at the same cross profile level. The tip of papillary muscle “p” is considered the vertex of the angle between the posterior annulus–tip of papillary muscle ray “p-a” and the first order chord of the anterior leaflet ray “p-e” during the end diastole “ filling angle”, and by implanting a ring annuloplasty this angle is narrowed. Thus, to obtain the filling angle wide as much as possible, the triangle a.p.e during the end diastole should be an equilateral triangle, so e-a (new chord) equal to e-p ( first order chord of anterior leaflet).