Angioscan Electronics AngioScan-01, User Manual, Page: 43 / 119

AngioScan Medical Tests 39
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4.1.4.10 AGI - Aging Index
Aging index (AGI) is an indicator of the relative amplitudes of the various components of the pulse wave.
One of the research methods used in calculating AGI is a mathematical analysis of the features of the
derivatives of the pulse wave. The various components of the pulse wave are most easily observed in the
second time derivative of the pulse wave.
The graph of the second derivative of the pulse wave has 5 distinct components (peaks):
· A – an initial positive peak;
·
B – an early negative peak;
· C – a middle “increasing” peak;
· D – a late “decreasing” peak;
·
T – a positive diastolic peak.
Mathematical derivative of the pulse wave at [Korpas et al. 2009].
The age index (AGI) is calculated as the difference between the amplitude of the early negative peak and
those of the other components to the amplitude of the initial positive peak: B-C-D-E / A [Hashimoto et al.
2005; Takazawa et al. 2007].
The age index is also used to assess the ratio between the direct and reflected components of the pulse
wave, and can be either positive or negative.
This index is highly correlated with the blood pressure and
the heart rate [Hashimoto et al. 2005; Simek et al. 2005]. Thus, an increase in blood pressure leads to
an increase in the age index. An increase in the heart rate leads to a decrease in AGI. Thus, at high
blood pressure the age index can be artificially high. When tachycardia is present, the AGI can be
artificially low.
In addition, there are age-related variations of the age index.