Angioscan Electronics AngioScan-01, Руководство пользователя

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© 2014 AngioScan-Electronics LLC
AngioScan Medical Tests
4.1.4.1 HR - Heart Rate
The pulse rate at the fingertip corresponds to the heart rate. The heart rate between 60 to 90 beats per
minute is considered normal [Braunwald's Heart Disease, 9th ed, 2012]. When evaluating the results of
the heart rate measurements it is important to consider the presence of the diseases that can lead to
changes in the heart rate and the therapies that can cause a reduction in the heart rate (for instance, the
beta-blockers).
An example of a clinical application of the heart rate parameter monitoring is during orthostatic test. To
evaluate the effect of an orthostatic test on the heart, the contour analysis of the pulse waves in the
supine position and after standing up should be conducted.
The magnitude of the difference in the heart
rate before and after standing up reflects the impact of the body position on the cardiovascular system.
This allows one to assess the functional status of the regulatory mechanisms and the vagotonic
reactions.
The pulse rate analysis also provides information about the fitness level of the patient and aids
in the detection of orthostatic hypotension.
Differences between the heart rate in the supine position and after standing up:
· 0 to 12 beats per minute (bpm) – healthy trained people;
·
from 13 to 18 bpm - healthy untrained people;
·
more than 20 bpm – excessive stress on the cardiovascular system indicating cardiovascular disease
or orthostatic hypotension.
4.1.4.2 AIp - Augmentation Index, peripheral
Peripheral augmentation is calculated as the difference between the amplitude of the second and that of
the first systolic peaks of the pressure pulse wave recorded during the contour analysis. Augmentation
index (AIp) is expressed as a percentage of the pulse pressure. This parameter reflects the contribution
of the reflected pressure waves to the arterial blood pressure and identifies the type of the pulse wave.
There are three types of pulse waves: A, B and C.
Augmentation pressure is the difference between the pressure of the first (T1) and second (T2) systolic
peaks of the pressure pulse wave. Augmentation pressure increases significantly with increasing arterial
stiffness causing an increase in the central arterial pressure and an increase in the afterload on the
myocardium of the left ventricle.
AIp index is calculated according to the following formula:
AIp = 100% * (D [T2] - D [T1]) / D [Tmax]
where D [Tn] is the amplitude of the pulse wave at time Tn.
The Type C pulse waves are typical for young people with healthy cardiovascular system. The Type C
pulse waves are formed when the blood vessels are healthy and elastic, and when the reflected pulse
waves reach the heart during the diastole or late systole. In this case, the maximum pressure of the
direct pulse wave is much greater than the maximum pressure of the reflected wave. The augmentation
index of the pulse waves of this type has a negative value.
When the arterial stiffness increases as a result of aging or disease, the reflected pulse waves reach the
heart during the systole. For instance, with age, the maximum pressure of the reflected wave gradually
achieves that of the direct wave and forms the Type B pulse wave, which can be visually characterized
as having a plateau on the top of the pulse wave. In this case, the augmentation index value is near zero,
reflecting the comparable pressures of the direct and the reflected pulse waves.
As the arteries continue to stiffen, the velocity of the reflected waves increases substantially. The
maximum pressure of the reflected wave becomes greater than the maximum pressure of the direct