The stiffness of normal and abnormal mitral valves.

Background: Although it is well known that valvular lesions show changes in stiffness, this fact has not been studied objectively or quantitatively.

Methods: Using a tactile sensor, stiffness of the mitral valve was measured at 11 autopsies and 19 surgically excised specimens. The relationships between stiffness and histological state were investigated in 394 points of resected specimens.

Results: In normal mitral valves, the anterior leaflet was significantly stiffer than the posterior leaflet in all zones. The rough zone had the least stiffness in both leaflets. Mitral stenotic valves were significantly stiffer than normal in all zones, the rough zone had the greatest stiffness. The grade of fibrosis (r=0.862), hyalinosis (r=0.783), and calcification (r=0.464) had positive correlation with the stiffness, respectively. An S score that was composed of these three factors had strong positive correlation (r=0.935). The regression equation was: stiffness=2.882+2.304xS score (r(2)=0.88). With cut-off values of 8 g/cm for severe fibrosis, 10 for focal hyalinosis, 13 for diffuse hyalinosis, 15 for mild calcification and 18 for massive calcification, these changes were accurately (>90%) detected. The grade of myxoid change had mild negative correlation with the stiffness (r=-0.507).

Conclusion: The actual value of stiffness of normal and abnormal mitral valves and the relationships between stiffness and histological changes were obtained. A tactile sensor promptly and accurately shows stiffness of the heart valve indicating its histological state. It can be a useful device for cardiovascular surgery.