Pathway for Elimination of Distance Measurement in Studies of Pulse Wave Velocity
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See related article, pp 937–945
The classic studies of Bramwell and Hill1 in 1922 relating elasticity of the artery wall to the speed of the traveling pulse wave led to measurement of pulse wave velocity (PWV) in large population groups to characterize age-related changes in arterial stiffness.2,3 These early studies, among others, all showed a general increase in PWV with age; however, there was substantial variation in values of aortic PWV at similar ages between populations of different ethnic origin and geographic location.4 Reasons for this are varied but include variable rates of vascular aging in different populations exposed to different environmental and dietary factors and variations in age-related increase in blood pressure. However, an important consideration is also the variation in methodology for measurement of pulse transit time and travel distance to compute PWV.
With high fidelity recordings of the arterial pulse, reproducible estimates of pulse transit time can be obtained by identifying a fiducial point close to the foot of the wave. For mechanical sensors, the dispersive nature of the skin and tissue overlying an artery generally attenuates high-frequency components, and so the foot of the pulse is not readily identified. This may have been a contributing factor to the variation in PWV determined by mechanical strain-type transducers in some of the early PWV studies. Notwithstanding the accuracy of pulse transit time estimation, its relation to arterial stiffness (and PWV) is determined by the path length traveled by the propagating pulse, a quantity which is not possible to measure with a certain degree of accuracy without physically visualizing the morphology of the arterial segments and branching structure. Hence, an estimate of the path length is obtained by large-scale linear distances on the body surface (Figure).