The Stiffness of Normal and Abnormal Mitral Valves

Original
Article

Kazuhito Imanaka, MD,^1,* Shinichi Takamoto, MD,¹ Toshiya Ohtsuka, MD,¹ Teruaki Oka, MD,² Akira Furuse, MD,³ and Sadao Omata, PhD⁴

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+2.304×S score (r²=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. (Ann Thorac Cardiovasc Surg 2007; 13: 178-184)

Key words: mitral valve, stiffness, tactile sensor

¹Department of Cardiothoracic Surgery and ²Department of Pathology, The University of Tokyo, Tokyo, ³JR Tokyo General Hospital, Tokyo, and ⁴College of Engineering, Nihon University, Fukushima, Japan. *Present affiliation: Department of Cardiovascular Surgery, Saitama Medical Center, Saitama, Japan.

Received June 16, 2006; accepted for publication September 9, 2006.
Address reprint requests to Kazuhito Imanaka, MD: Department of Cardiovascular Surgery, Saitama Medical Center, Kamoda 1981, Kawagoe, Saitama 350–8550, Japan.