Characteristics of Impact and Pulse Wave Propagation in Brachial and Radial Arteries

¹ From the Gerontology Branch, National Heart Institute, National Institutes of Health, Bethesda, and the Baltimore City Hospitals, Baltimore, Maryland

Externally induced impact waves may be propagated along the living artery. Such transients are often followed by a ‘free vibration,’ which, with adequate recording, exhibits a natural frequency of the order of 30–45 cycles per second and often appears underdamped. These transients are modified in transmission over the brachioradial arterial segment. The velocity of impact waves, like the velocity of cardiac pulse waves, is pressure dependent. This relation has been analyzed in detail for a group of males. In general, the change in velocity with pressure is large in comparison to differences between inividuals at the same pressure. An averaged relation between pressure (p) mm Hg, and velocity (v) m/sec., for 94 subjects is given as v² = – (27 ± 19) + (4.9 ± .4)p – (.0083 ± .0018)p². From this description, together with stated assumptions about the interpretation of wave velocity, the pressure-volume relation of this artery is developed. From this, and stated dimensional assumptions, a stress-strain curve is presented. The equivalent modulus of elasticity is calculated to be 0.1 – 3.4 x 10⁷ dynes/cm², for the type of stress used in these studies. The velocity of impact waves at diastolic pressure is shown to be greater than the velocity of cardiac pulse waves.