pressure waveforms were defined in terms of their morphological
differences and separated into different types. Peak systolic pressure
pulse pressure (PP), pressure at inflection
and the augmented pressure,
are defined. Systolic pressure
and the corresponding augmentation index is given by
Although the augmentation index has been used to represent the
it is not equivalent to the reflection
merely a single number and does not represent
the frequency content of the reflected wave.
Wave Reflection Sites
Wave reflection sites exist all over the systemic arterial tree, due to
branching, and impedance
mismatching at arterial terminations.
Therefore, reflections cannot
originate from one site only.
Indeed, there is no agreement on the
location of reflecting sites. Some suggest that the major reflection site as
seen from the proximal aorta, appears to be in the region of the pelvis or
the aorto-iliac branching junction. Others, however, suggest that the first
major potential reflecting site
at the aortic arch. Although there is no
major agreement on the reflecting sites, the arterioles are recognized
being the principal sites for wave reflection, and the reflection coefficient
as being high.
There are multiple reflection sites and the effects of
reflections on pressure
and flow waveforms
investigated (Berger et al.,
The model-based analysis showed
how the forward and reflected waves are actually the summations
repeated antegrade and retrograde waves.
The dispersion of such
multiple reflections make direct measurement and quantification of their