Non-invasive assessment of aortic mechanical properties.

Echocardiography and sphygmomanometry were used to noninvasively assess the changes in aortic mechanical properties associated with aging. Fifty normal individuals were examined and were divided into three groups: young (less than 35 years of age), middle-aged (35-55), and old (greater than 55). Experimental measurements indicated that elastic aortic stiffness in the circumferential direction increased with increased age. It was concluded that this was consistent with increased deposition of circumferentially oriented collagen within the media. Associated with increased elastic aortic stiffness in the circumferential direction was a decrease in the ability of the aorta to act as an auxiliary pump. The average work per unit length recovered from aortas of older individuals was only 44% of that recovered from the aortas of individuals in the young group. These studies suggest that increased elastic aortic stiffness results in decreased aortic pumping efficiency and may lead to a compensating increase in blood pressure.