Multiple Wave Reflections In The Systemic Arterial System

Pressure and flow waves measured in the aorta can be decomposed into one foryard and one backward traveling component. In this paper we postulate that the forward and backward waves are not single waveforms. but are themselves composed of individual antegrade and retrograde waves. The antegrade waves include the initial waveforms (produced in the absence of reflection) and those arising from reflections at the aortic valve while the retrograde waves are produced by reflections in the periphery. Modeling the arterial system as an equivalent single tube terminating in a complex load, we derive expressions relating the measured waveforms with the initial waveforms, reflection coefficients, and properties of the arterial system. Results indicate that multiple wave reflection does occur with the waves decreasing in amplitude as reflection continues. In addition, it appears that individual reflections tend to become insignificant before the onset of the next cardiac cycle.