Pulse wave velocity, or PWV, describes how fast the pressure and flow pulse from each heartbeat travels along the arteries. A common way to estimate PWV is to measure the pulse at two locations and compute distance divided by transit time. PWV is widely used because it correlates with arterial stiffness. When arteries are stiffer, the pulse travels faster [1].
In the aorta of a healthy subject, PWV is typically around 4 to 5 m/s [2]. In the pulmonary circulation, values around 3.5 m/s at a mean pulmonary artery pressure (mPAP) of 13 mmHg and around 10 m/s at an mPAP of 50 mmHg have been reported [3].
PWV reflects wave propagation in a coupled system of blood and vessel wall. When pressure rises, the artery expands slightly and stores energy. This wall expansion strongly influences how the wave travels and therefore affects the wave speed.
If the arterial wall becomes stiffer, it expands less for the same pressure change. Reduced expansion leads to faster wave propagation. This helps explain why PWV often increases with age and with conditions that stiffen the arterial wall.
A useful thought experiment is to imagine vessels made of steel. In a very stiff tube, wall expansion becomes negligible. The dominant remaining contribution then comes from the compressibility of the fluid, so the wave speed approaches the speed of sound in that fluid. Real arteries remain far from this rigid limit, which is why physiological PWV is much lower than the sound speed in blood.
[1] Bramwell, J. Crighton, and Archibald Vivian Hill. “The velocity of pulse wave in man.” Proceedings of the Royal Society of London. Series B, Containing Papers of a Biological Character 93.652 (1922): 298-306.
[2] Westerhof N., Stergiopulos N., Noble M. I. M., Westerhof B. E. (2019). Snapshots of Hemodynamics: An Aid for Clinical Research and Graduate Education, Vol. 3rd eds Westerhof N., Stergiopulos N., Noble M. I. M., Westerhof B. E. (New York, NY: Springer International Publishing AG; )
[3] Kopeć G, Moertl D, Jankowski P, Tyrka A, Sobień B, Podolec P. Pulmonary artery pulse wave velocity in idiopathic pulmonary arterial hypertension. Can J Cardiol. 2013;29(6):683-690. doi:10.1016/j.cjca.2012.09.019