Angioscan Electronics AngioScan-01, Руководство пользователя

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© 2014 AngioScan-Electronics LLC
AngioScan Medical Tests
4.1.4.22 TdVMax - Time of maximum blood filling rate
4.2 Occlusion Test
An occlusion test is simple and non-invasive. During the test, there is a complete clamping of one of the
peripheral arteries for a few minutes. In response to the occlusion, after the clamping has been released,
there is a change in the of blood flow distal to the site of compression.
The most characteristic changes occurring after an occlusion are a modified capillary finger blood flow
and a decrease in the pulse wave velocity.
The magnitude of the changes in the blood flow allows one to evaluate endothelial function of small
resistive arteries and arterioles.
A change in the pulse wave velocity, i.e. the phase shift, is determined by the influence of nitric oxide in
the smooth muscle cells of the arterial wall of large muscular arteries (brachial and radial artery).
Nitrogen monoxide reduces the tone of the arteries and the surrounding muscles, which leads to a
reduction of pulse wave velocity and a change in the pulse wave shape.
An occlusion test has the following characteristics:
·
Effective in early detection of dysfunction in the cardiovascular system
·
Safe for the patient
·
No medical contraindications
·
Easy to implement and does not require a medical training
·
Does not require any special testing conditions
An occlusion test or a reactive hyperemia test is used to assess the endothelial function of blood
vessels. Endothelial dysfunction is a strong independent predictor of cardiovascular events in high risk
patients, including the elderly, patients with hypertension, atherosclerotic peripheral vascular disease
and in patients undergoing percutaneous coronary intervention [Halcox et al. 2009]. In these diseases
and conditions, endothelial dysfunction is often a cause, and a marker of local inflammation and a high
prothrombotic potential of the arterial wall, which increases the risk of destabilization of atherosclerotic
plaques and the development of an arterial thrombosis. The results of large-scale experimental work
suggest that endothelial dysfunction strongly correlated with other cardiovascular risk factors such as
diabetes mellitus, body mass index, high levels of total cholesterol and low-density lipoprotein and
smoking [Halcox et al. 2009; Hamburg et al. 2008; Bonetti et al. 2004; Lind et al. 2005].
The test sequence for the occlusion test includes several steps. First, the Angioscan device
automatically measures the blood pressure of the patient (this feature is not available in some models of
the device). In the next step, the baseline pulse waves are collected for several minutes. After the
recording of the pre-occlusion or baseline pulse waves, the cuff is inflated (either automatically or
manually by the operator) to a suprasystolic pressure (for instance, the systolic blood pressure plus 50
mmHg). The suprasystolic pressure completely blocks the blood flow in the brachial artery.
The suprasystolic pressure is maintained in the cuff for 5 minutes, then the cuff is rapidly deflated. After
the cuff pressure is released, the pulse waves are recorded for several minutes. Upon completion of the
test, the Angioscan software automatically calculates the increase in the amplitude of pulse waves after
the occlusion of the brachial artery. A post-occlusion increase in the amplitude of pulse waves of two
times or more of that before the occlusion indicates a normal function of vascular endothelium.
An example of an occlusion test data in a subject with a normal endothelial function.