| What does the test involve? |
|
| The purpose of measuring HRV is to examine
the efficacy of the cardiac autonomic system. Measuring HRV
on its own provides an indication of risk of heart disease,
but it does not tell the full story. To see if the sympathetic
and parasympathetic nervous systems are functioning effectively,
we need to force it to act. |
| |
In normal usage asking the patient to
perform what is known as an orthostatic test easily does this.
This was originally performed by the “tilt table”
but research has shown that the lying-standing-lying protocol
is just as effective. This simply means asking you to wear the
TF5 chest harness and to lie down on a couch for 5 minutes,
stand up for 5 minutes and then lie down for a further 5 minutes.
When the patient is lying down, the heart needs to work less,
as it does not need to pump blood against gravity to the oxygen
demanding brain. In this instance, the parasympathetic system
is active and slows the heart rate. When the subject stands,
less blood reaches the brain due to gravity, thus causing lower
blood pressure in the carotid arteries in the neck. The baroreceptors
(special sensing organs that measure blood pressure) located
in these arteries provide feedback to the autonomic system causing
the sympathetic nerve to become more active and the parasympathetic
nerve to dampen. Lying down again reverses the action.
The TF5 graphical representation of these actions can clearly
indicate the degree of cardiac autonomic function and greatly
enhances the doctor’s ability to analyse the functionality
of the control mechanisms of the heart. |
| |
| Why 5 minutes for each test? |
| The TF5 is based on the recommendations
of the “Special Task Force” of the European Society
of Electrophysiology and the North American Society of Pacing.
There have been several scientific papers showing that the repeatability
of frequency domain analysis of HRV is comparable to that of
the traditional 24 hour Holter monitor tests. These scientific
papers demonstrated that the repeatability of short-term frequency
domain tests were acceptable for even 2 minute tests. However,
for safety and to ensure data quality, the Task Force recommended
that short-term tests should be of 5 minutes duration. The 5-minute
protocol was also recommended as a standard to allow comparison
of research or clinical papers. |
|
All material contained
within this website is copyrighted to Advanced Medical
Diagnostic Group Limited.
VariaCardio® and VariaPulse are registered trademarks
of AMDG Ltd. This product is protected by patents owned
by AMDG Ltd.
Manufactured for AMDG by MIE Medical Research Ltd (an
ISO13488 accredited company). AMDG and MIE Research Ltd
reserve the right to amend specifications without notice
in accordance to their policy of continual product improvement. |
| |
| © 2001-5 Advanced Medical Diagnostics Group Ltd. All Rights Reserved. |
| |
| AMDG Ltd,
6 Wortley Moor Road, Leeds, LS12 4JF
Tel: +44 (0) 113
279 1010 Fax: +44
(0) 113 231 0820
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