The Effect of Variation of Longitudinal Stretch on the Dynamic Elastic Properties of Isolated Segments of Canine Carotid Arteries

Isolated canine carotid arterial segments were subjected to small constant amplitude pressure fluctuations, and the frequency responses of the radial displacements were obtained. These frequency responses, which exhibited a flat low-frequency portion followed by at least two resonance peaks, were measured at several elongations and transmural pressures. Static and dynamic circumferential elastic moduli were calculated and showed a direct dependence on increasing transmural pressure, whereas the dependence on longitudinal elongation was absent. At elongations greater than natural, the frequencies at which resonance occurred increased with increased transmural pressure; however, measurements of longitudinal tensions at varying elongations and transmural pressures suggests a closer relationship between longitudinal tension and the frequencies at which resonance occurs. This implies that the mode of vibration at resonance is similar to the transverse vibration of a string. This idea was supported by calculation of the frequency response of arterial segments using the vibrating string mode. This gave close agreement to the experimental results, whereas there was no such agreement between calculated curves based on the dilatational mode and the experimental results.