Alterations with Age in the Viscoelastic Properties of Human Arterial Walls

The circumferential incremental Young's modulus was measured in 59 major arteries of both "young" (less than 35 years of age) and "old" (greater than 35 years of age) subjects. Dynamic measurements of wall elasticity and viscosity were made which indicated a high viscosity in the femoral arteries. This was attributed to their high content of muscle. Although the "young" group showed, at any given pressure, an increasing wall stiffness towards the periphery, in "old" arteries, an opposite trend was found. When dimensional changes (radius and wall thickness) in the "old" group were considered it was apparent that at all sites the arterial wall tissue became weaker with age. Nevertheless, as a consequence of these dimensional changes the impedance characteristics of the old arterial tree still retained the nonuniformity (an increase towards the periphery) of the "young" which has considerable haemodynamic advantage.