Endothelial Dysfunction Test

What do the diseases below all have in common? Read on to find out.

 

All of these disease share one common factor:

What is Endothelial Dysfunction?

Endothelial Dysfunction is the most common form of vascular abnormality. Endothelial cells form the inner lining of blood vessels. Each artery has three layers: the endothelial layer (inner most), the medial layer, and the adventitial layer (outer most). The endothelial layer, being the inner most layer, has been referred to as the “brain” of the arteries and is considered the most important layer.

Anatomy of an Artery (2)
Tunica Adventitia (3)

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What is endothelial function?

“Endothelial Function” is a misnomer! The vascular endothelial cells have multiple functions, which are:

  1. Regulates fluid and molecule traffic between blood and tissues
  2. Serves as an anti-coagulant (anti-clotting) surface
  3. Contributes to vascular homeostasis and repair
  4. Plays a central role in angiogenesis and tissue wound healing
  5. Plays a vital role in vascular tone and blood flow regulation*

*Assessing this last function is the most practical way of measuring endothelial function.

Endothelial function is the most important function of the vascular system. The most well-known and visible function of endothelial cells is the ability to increase blood supply by dilating the artery when needed. Vascular resistance decreases to bring more blood flow to tissues as the arterial lumen diameter increases. This ability is also referred to as “vascular reactivity,” which denotes the competency of the vascular system to respond quickly and deliver more blood to organs when needed. Good vascular reactivity is seen where the arteries are fully dilated to allow high volume blood flow, versus poor vascular reactivity where the arteries do not dilate enough to increase blood flow.

Vascular reactivity is the most important element of vascular function, therefore the phrases “impaired vascular reactivity,” “vascular dysfunction,” and “endothelial dysfunction” may be used interchangeably.


What Causes endothelial dysfunction?

Negatively affected by:

  • Smoking
  • Diabetes
  • High blood pressure
  • High Cholesterol
  • Weight gain
  • Mental stress
  • Excessive inflammation

Positively affected by:

  • Exercise
  • Weight loss
  • Stress reduction
  • Cholesterol-lowering drugs

There are a number of factors that intoxicate endothelial cells and impair their function.

Risk Factors:

  • Excessive inflammation
  • Mental stress
  • Weight Gain
  • High cholesterol
  • High blood pressure
  • Diabetes
  • Smoking

Protective Factor:

  • Cholesterol-lowering drugs
  • Stress reduction
  • Weight loss
  • Exercise

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2 Natural Course of Atherosclerotic CVD 72 CENEGENICS PHOENIX


How is endothelial function measured?

In clinical cardiology research laboratories endothelial function was first measured by injecting acetylcholine via catheter into the coronary artery and monitoring the response by X-Ray imaging, specifically measuring the diameter change of the artery. If the coronary artery diameter increases, it indicates a healthy endothelial function.

However, if the coronary artery diameter decreases, it is a clear indication of endothelial dysfunction and sign of atherosclerosis. Obviously this technique is very invasive and requires hospitalization. It is also very expensive and is not justified for patients who are asymptomatic or currently healthy. In 1992 scientists developed a research technique for assessing endothelial dysfunction using high resolution ultrasound imaging of the brachial artery.

This technique requires a five-minute occlusion and release of the brachial artery blood flow using a blood pressure cuff, also called a reactive hyperemia procedure and manually measuring the diameter of the brachial artery using a high frequency ultrasonic imaging probe. If the brachial artery diameter increases less than 5% it indicates endothelial dysfunction and a sign of cardiovascular disease. However, if the brachial artery diameter increases more than 10% it is a clear indication of healthy endothelial function.

Although this discovery was a major step forward and is a useful tool for research laboratories, it lacks feasibility for use in clinical practice in doctors’ offices mainly because it requires high resolution ultrasound imaging and an experienced sonographer. Also this method is operator dependent and is sensitive to the arm’s position, leading to inconsistent results and unacceptable variations.

Reactive Hyperemia (2)What is reactive hyperemia? And how do we measure vascular reactivity and endothelial function? Using an arm cuff reactive hyperemia procedure. Reactive hyperemia is the transient increase of blood flow that occurs following a brief period of ischemia, or blood flow occlusion.

In a classic reactive hyperemia test an arm cuff occludes the brachial artery and stops blood flow for five minutes resulting in a tissue hypoxia or anaerobic metabolism.

During cuff inflation, blood flow stops and tissue becomes ischemic, leading to an accumulation of lactates and other chemicals cause the vessels in this area that to dilate.

Blood flow increases 2 to 3 times after releasing the cuff. This reactive hyperemia response is largely dependent on endothelial cells. The healthier the artery, the larger the reactive hyperemic response.

Cenegenics now uses the Vendys machine to measure the hyperemic response. Vendys (Vascular Endothelial Dysfunction) is the only FDA cleared, fully automated, operator independent, non-invasive, easy to use, office based device for measurement of vascular reactivity and endothelial function.


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How does it work?

Vendys uses smart temperature sensors at the fingertip and algorithms to measure vascular reactivity. It is non-invasive, inexpensive, and easy to use. Similar to the ultrasound based measurement, Vendys uses a five-minute arm cuff occlusion reactive hyperemia procedure. The Vendys test begins with an automated blood pressure measurement followed by a tightening of the arm cuff on the right arm. During the cuff occlusion period, fingertip temperature in the right hand falls due to the absence of warm circulating blood. Once the cuff is released, blood flow rushes into the forearm and hand, causing a temperature rebound in the fingertip, which is directly proportional to the vascular reactivity. Because blood is warm, the more blood flow, the higher the temperature at the fingertip. The higher the temperature rebound, the better the vascular function.

 

 

What are the advantages of using this device?

No need for an expensive high resolution ultrasound imaging technology or an experienced sonographer. Vendys testing can be done in any doctor’s office or point of care clinic.

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Dr. C.B. Daniel Cenegenics AZ Elite Health and Age Management
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