Angioscan Electronics AngioScan-01, User Manual, Page: 35 / 119

AngioScan Medical Tests 31
© 2014 AngioScan-Electronics LLC
wave. As a result, the Type A pulse wave is formed with a pointed apex, corresponding to high pressure
augmentation. In this situation, augmentation index has positive value. The higher the stiffness of the
arterial wall, the greater the value AIp.
In assessing the augmentation index, it is essential not only to look at its absolute value but also the
sign of the indicator. Some increase in vascular stiffness can occur in older healthy people with natural
aging process of the vascular system. Normal age-adjusted augmentation index values are presented in
the table below.
Age
The average value AIp, %
The lower interval AIp, % Upper interval AIp, %
20 -4.67 -23.27 16.87
30 3.03 -15.57 24.57
40 10.73 -7.87 32.27
50 18.43 -0.17 39.97
60 26.13 7.53 47.67
70 33.83 15.23 55.37
80 41.53 22.93 63.07
4.1.4.3 AIp75 - Augmentation Index normalized to heart rate of 75 beats per minute
A large amount of clinical evidence has been accumulated that demonstrates that the increase in
augmentation index is significantly associated with an increased risk of overall mortality and mortality
from diseases of the cardiovascular system, as well as with the risk of cardiovascular events
[Londonetal,
2001; Weberetal, 2005; Willus-Hansenetal, 2006].
Augmentation index depends on the heart rate. This is due to the fact that the first harmonic of the pulse
wave uses most (up to 60-70%) of the total energy of the heart muscle contraction.
Therefore, the first
harmonic, and therefore, the pulse rate (or the heart rate) makes the most significant contribution to the
augmentation of pulse pressure.
In order to compare AI values for different heart rates, aheart rate adjusted augmentation index AIp75 is
calculated. On average, when heart rate increases by 10 bpm, AIp decreases by 5%. This ratio is used
to convert an AIp value into AIp75.
This parameter is useful, for instance, when taking several measurements over time in order to monitor
the change in the stiffness of the arteries during an antihypertensive therapy.
4.1.4.4 CT - Pulse wave Contour Type
Depending on the pulse wave velocity and central blood pressure, pulse waves can be categorized into
three types A, B and C.
Healthy arteries are elastic and the pulse waves, when reflected from the sites where major arteries
bifurcate, reach the heart after the aortic valve closure, during diastole and late systole, thus decreasing
the afterload on the myocardium of the left ventricle, and improving coronary perfusion. In such healthy
elastic arteries, the pulse waves are of type C. Type C pulse waves have two clearly visible peaks. The
first peak corresponds to the direct wave. The second peak, which is much smaller in amplitude,
corresponds to the reflected wave. This type of pulse wave is typical for young people, with no clinically