It seems that recently the interest in the role of pulse wave reflection in the arterial system has been amplified. In recognition of the effect of wave reflection a new pulse-related „amplification index“ was introduced for diagnostic purpose.
Besides these historical remarks it seems interesting to discuss some special aspects of wave reflection in arteries. Any location in elastic tubes where the mechanical properties or the dimension changes gives rise to reflection of pressure and flow waves. In the periphery of the arteries the reflection usually is positive. The increase of the pressure amplitude towards the periphery is due to reflection and to the effect of tapering of the arteries. Since the pressure-flow-relation in the peripheral resistance vessels is nonlinear, the magnitude of the reflection factor depends on the pressure level. In locations where an artery is collapsed, e.g. by a pressure cuff, remarkable changes of the reflection factor from positive to negative during the time of the transient of one pulse can be observed. Reflected waves returning from a peripheral artery, e.g. from the upper extremity, are reflected negatively when arriving at the branching point from the aorta. A particular note has to be made with respect to the repercussion of reflected waves on the heart. Consequences thereof are the questions concerning optimization of heartbeat and adjustment between heart and arterial system.
We have observed that the magnitude of the reflection factor may vary from beat to beat. One attempt to interpret this phenomenon is the assumption of interference between slow variations of resistance and pressure and fast cardio-ballistic vibrations in the vicinity of arteries, particularly in extremities.
E. Wetterer and T. Kenner: Dynamik des Arterienpulses. Springer 1968
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