Abstract
Pathology of aortic valve sclerosis is very similar to that of atherosclerosis and it seems to be one of inflammatory changes caused by damage to endothelium of the aortic valve. However, stress factors of the damage have not been clarified yet. This study focused on both aging and hypertension as the highest risk factor of the valve sclerosis and supposed that local mechanical strain on the valvular surface occurred by valve opening and closing behavior with heartbeat is one of the mechanical trigger for inflammatory. So, in order to clarify the pathogenic mechanism, in vitro experiment using a realistic aortic valve model and a cardiovascular flow simulator was conducted and spatial-temporal distribution of the strain on the leaflet was measured by 3D shape measuring technique. As the result, the areas at the centre of the leaflet and the boundary between the leaflet and Valsalva sinus strained locally much larger than the other area during diastole. And tensile strain on the whole leaflet enlarged with increasing pressure load on the valve. On the other hand, the areas in the vicinity of the boundary with the sinus including valve commissures were bent locally during systole and then the bending strain at the area was almost constant. These results indicated that either tensile strain or bending strain is continuously occurred on the valvular surface during a cardiac period. And these high strain areas on the leaflet model were very similar to the place where lipid deposition as a stage prior to sclerosis by the hyper-cholesterol loaded animal experiment using a rabbit of the normal blood pressure. Therefore, this result suggests the local high strain is one of the important mechanical stress for the valve sclerosis occurring.
