Biomechanical Study of Vascular Walls

Mechanical properties of vascular walls are very important in the field of medical research since cardio-vascular diseases are closely related with them. They also may provide some suggestion in the field of engineering because vascular walls are considered to be one of the ideal composite materials. In order to examine them, the authors made an apparatus for testing the mechanical behavior of vascular walls, and its details are described in the present report. With this apparatus, oscillating pressure superimposed upon a constant pressure can be loaded on the specimen. Its intraluminal pressure and diameter can be measured simultaneously and continuously. From its performance test, it was confirmed that the testing apparatus can be used efficiently for examining not only the static but also the dynamic mechanical properties of vascular walls. Vascular walls are generally constituted of three structural components. Therefore, it is necessary to determine the volume or area fraction of each component occupied in a wall exactly before discussing their mechanical properties in terms of vascular structure. The following method is proposed here for their determination. Some thin slices are sectioned out from a specimen whose shape and structure have been fixed under a constant pressure level. Each sectioned slice is stained by such a way as only one of the three components is distinguishable in the section. Area fraction is calculated from the density distribution profile obtained by scanning the photograph of the stained structure by a microphotometer. Sufficiently good results have been obtained by this method. It is expected that some generalized constitutive laws of vascular walls may be established by using the apparatus and the method presented in this report.