ABC of Vascular Disease
Ambulatory Venous Pressure (AVP)
Ambulatory venous pressure (AVP) is the "gold standard" test of the efficiency of the calf musculovenous pump. It is performed by placing a small needle into one of the veins on the back of the foot and connecting the needle to a blood pressure measurement machine. The test has three parts:
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The subject is then asked to stand up and the standing venous pressure is measured.
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The subject is asked to perform ten heel raise exercises to work the muscluovenous pump and the ambulatory venous pressure (AVP) is recorded.
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The subject is asked to rest again in the standing position and the rate at which the ambulatory pressure returns to the standing pressure is measured, called the refilling time.
Normal Result
In a normal subject the standing venous pressure is around 90 mmHg
(depending on their height). During exercise this should fall to around 30
mmHg and after exercise this should only rise slowly over half a minute or so
back to the standing pressure.
Abnormal Result
There are a number of possible abnormal results:
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The pressure does not fall normally during exercise, which indicates that the calf pump is not working effectively. There are many causes for this. |
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The pressure rises rather than falls during exercise, which indicates that the deep veins are occluded. |
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The AVP returns to the standing pressure too quickly, which indicates reflux in either the deep or superficial veins due to absent or damaged valves. |
The greater the ambulatory venous pressure (AVP) the more
severe the problem with the musculovenous pump and the more likely the subject
will suffer from leg ulcers.
AVP measurement is a specialist, invasive test which is only performed in
patients with clinical evidence of chronic venous insufficiency (CEAP
3-6). Photoplethysmography is used
as an alternative in patients with varicose veins only (CEAP 2). The
results of the AVP (or PPG) and other tests such as venous duplex
ultrasound or venography are complementary.
© S.R.Dodds 2001