‘This may be the future’...
(The following article was just pasted on to the Yahoo/HDII thread under the same title. Bolding is mine.)
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Studies of Blood Vessel Elasticity May Better Define Risk for Cardiovascular Disease
April 17, 2001
A new device that measures the stiffness of blood vessels as blood courses through them is helping doctors at the Medical College of Georgia determine whether a hormone secreted by the lining of these vessels affects their elasticity.
Endothelin, secreted by the endothelial cells inside blood vessels, is a powerful vasoconstrictor, said Dr. L. Michael Prisant, cardiologist and hypertension specialist at MCG and a 1977 graduate of the School of Medicine.
He and Dr. Adviye Ergul, a vascular biologist at MCG and the University of Georgia, are using a research version of the Cardiovascular Profilor (SJ note: this is research version of the FDA-approved CVProfilor, the proprietary device sold by Hypertension Diagnostics) to determine if there is a difference between the vascular compliance or arterial elasticity of the blood vessels of blacks and whites and, if so, whether endothelin plays a role.
The Profilor uses a piezoelectric crystal to convert the mechanical movement of the blood vessel to electrical energy and determine the level of elasticity. Corresponding endothelin levels are measured from a blood sample.
"Feel your own pulse," Dr. Prisant said. "Feel how it pushes against you. Now imagine if you had a lever to magnify that. That's what this device does; it magnifies it so you can see it, then calculates elasticity based on how much the blood vessels move up and down and the blood pressure."
We published before that endothelin is especially elevated in African-Americans with hypertension," Dr. Ergul said. "Now we want to see what the endothelin is actually doing. Right now, all we know is that the level is high. But what does that mean?" Dr. Ergul said.
She also is working with researchers at MCG's Georgia Prevention Institute to see whether this vasoconstrictor contributes to the development of hypertension; the work with Dr. Prisant focuses more on its potential role in maintaining an elevated pressure.
Previous studies at MCG and elsewhere using the Profilor have documented that reduced vascular elasticity goes hand–in-hand with hypertension. It's well-documented that blacks tend to have more severe hypertension and to have it younger in life.
Drs. Prisant and Ergul and study coordinator Dena Jupin are using the research version of the Cardiovascular Profilor – a similar version was recently approved by the Food and Drug Administration – to look at four populations of patients: blacks with normal blood pressure, hypertensive blacks on no medication and the same two categories of whites.
Previous studies required for FDA approval also compared four populations: adults without hypertension or a family history of the disease, adults without hypertension but with a family history, hypertensives whose blood pressure was under control and hypertensives without good control.
MCG was one of three centers to study these respective populations and find that each had progressively less elasticity; the uncontrolled hypertensives had the least elastic blood vessels.
Another study under way is comparing different ways of using the Cardiovascular Profilor. It's recommended that the blood pressure cuff be placed on the left arm and the transducer with the crystal be placed on the right. But MCG is looking at whether the arm matters by swapping the recommended location as well as putting both devices on one arm. This study provides additional information about how best to use the Profilor and may benefit patients who have medical conditions that prohibit using one arm, Dr. Prisant said.
Planned studies using the device will explore the impact of two popular antihypertensive drugs on the flexibility of blood vessels.
"This new device gives us a way to look directly at the blood vessel which is the target for all cardiovascular risk factors," Dr. Prisant said. He hopes it will ultimately provide a more targeted audience for blood pressure treatment. "Right now, all epidemiologic data regarding hypertension are based on office measurement of blood pressure. From looking at large numbers of patients we know the general rule is the higher the blood pressure, the greater the incidence of cardiovascular events. But there are a lot of things we don't understand and what is normal blood pressure for you may not be normal for me."
And, evidence is building that elasticity of blood vessels may be key to whether an elevated reading from a blood pressure cuff translates into a significant risk factor for cardiovascular disease.
"We know that if you have a normal blood pressure, but you have a first-degree relative who has high blood pressure, your blood vessels are less elastic," Ms. Jupin said. Also, smokers and diabetics typically have less elastic blood vessels, Dr. Prisant said.
Even with the accumulating information about the importance of elasticity, it remains common practice – and Dr. Prisant's practice – to prescribe antihypertensives to patients with a documented, elevated blood pressure, using the standard cuff alone.
But he says that the ability to look directly at blood vessels may one day better predict who would benefit the most from medication to regulate blood pressure. "This may be the future," he said
For more information about studies of arterial elasticity, contact Ms. Jupin at (706) 721-7903.
Copyright 2002/Medical College of Georgia/All rights reserved.
mcg.edu
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(from a publication of the Medical College of Georgia) |
