Basic principles that determine relationships between pulsatile hemodynamic phenomena and function of elastic vessels

Elasticity of arteries is a fundamental structural property that is a major determinant of the relationship of the pulsatile components of arterial blood pressure and flow. The basic periodic nature of cardiac contraction enables the oscillatory phenomena of blood pressure and flow to be represented in the frequency domain by decomposing time-varying pressure and flow signals into their harmonic components. This allows the calculation of vascular impedance and indices of wave propagation. Vascular impedance quantifies the relation between the magnitude and phase of the oscillations of pressure and flow, whereas wave propagation quantifies the change in amplitude and time delay of wave travel between two arterial sites. Arterial stiffness plays a central role in vascular impedance and wave propagation through the elastic properties of the conduit vessels. This chapter addresses these fundamental relationships through basic qualitative descriptions of underlying biophysical concepts, supported by formal equations where necessary for quantitative illustration of interrelationships of relevant parameters. The basic hemodynamic principles described in this chapter are aimed to support the specific areas addressed in other chapters of this textbook. Where appropriate, and to avoid excessive repetition, reference will be made to other relevant sections and chapters for further details.