Aortic wave reflection analysis: hydraulic and mathematical model study

Pressure and flow have been measured simultaneously at 6 locations along the aorta of a 1:1 elastic tube model of the arterial tree. The location of the input impedance minimum and the comparison of foot-to-foot (c_ff) and apparent phase velocity (c_app ) suggest a discrete reflection point at the level of the renal arteries, in accordance with literature. However, wave separation at the 6 locations in an incident and reflected wave does not reveal a clear picture. A reflected wave is generated at each location as the forward wave passes by indicating a continuous reflection. Further analysis is performed on a mathematical transmission line model. Simulating 3 reduced aortic models: (i) uniform tube; (ii) 2 tubes in series. With a sudden diameter reduction at the level of the renal arteries (iii) tapering tube. The input impedance of the tapered tube suggests a discrete reflection point at the level of the renal arteries. However. The pattern of incident and reflected wave in the tapering model corresponds to the hydraulic model observations of a continuous reflection. The discrepancy between c_ff and c_app can not be explained with any of the reduced aorta models. The authors conclude that the aortic wave reflection phenomena are at least in part determined by the tapering nature of the aorta