Endothelial Function Test2

The causes and progression of vascular disease are intimately related to the health of the inner lining of the arterial wall - the endothelium. The arteries are made up of three layers. The outer layer is mostly connective tissue and provides structure to the other two layers. The middle layer is the smooth muscle; it contracts and dilates to control blood flow and maintain blood pressure. The inner lining consists of a very thin, single layer of cells called endothelium, which provides a smooth protective surface. The cells that from the endothelium are called endothelial cells. These endothelial cells are in direct contact with blood.

Endothelial cells line the entire circulatory system from the heart to the smallest capillaries. These cells have very direct distinct and unique functions that are paramount to vascular biology.

Abnormal endothelial function (as called endothelial dysfunction) is a systemic pathological state of the endothelium   and can be broadly defined as an imbalance between the vasodilating and vasoconstricting substances produced by or acting on the endothelium. Normal functions of the endothelial cells include regulation of coagulation, platelet adhesion, immune function, and control of volume and electrolye content of the intravascular and extravascular spaces.

Endothelial dysfunction is a major physiopathological mechanism that leads towards coronary artery disease, and other atherosclerotic diseases. Many atherogenic factors, if left unchecked, damage the delicate endothelial cells. This damage leads to endothelial dysfunction and ultimately allows lipids and toxins to penetrate the endothelial layer and enter the arterial wall. This results in the initiation of an oxidative and inflammatory cascade that culminates in the development of plaque deposits (atherosclerosis). Subsequently, these plaques grow and begin to calcify. Some have fibrous caps that become thin and unstable. This may cause a plaque to rupture into the lumen and potentially clogs the artery with blood clot causing a heart attack.

Numerous factors cause endothelial dysfunction:

- Elevated LDL cholesterol. High LDL is dangerous because it can penetrate the endothelial wall, become oxydized and lead to the formation of foam cells, which form the core of a plaque deposit. Oxidized LDL cholesterol triggers an inflammatory process that accelerates vacular disease.

- Low HDL cholesterol. HDL protects against vascular disease by its anti-oxidant properties and by transporting the cholesterol from the arterial wall back to the liver for disposal through a process known as reverse cholesterol transport. If HDL levels are low, reverse cholesterol transports becomes impaired, allowing for increased accumulation of cholesterol in the arterial wall.

- High triglycerides. Elevated triglycerides cause increased CEPT activity which leads to increase in the number of LDL particles and smaller dense LDL. Both contribute to more plaque deposits.

- Oxidized LDL. The oxidation of LDL cholesterol in the arterial wall causes severe vascular damage. Oxidized LDL contributes to the entire atherosclerotic process, from start to finish.

- High blood pressure. High blood pressure can cause direct physical injury to the endothelial cells.

- Smoking. Smoking causes direct injury to the endothelium. Denudation of the endothelium causes the arterial wall to become more permeable to LDL cholesterol.

- Elevated C-reactive protein. Inflammation is central to the endothelial dysfunction that underlies atherosclerosis.

- Diabetes. Elevated blood glucose and insulin cause microvascular damage that cause endothelial dysfunction and accelarates atherosclerosis.

- Metabolic syndrome. All the components of metabolic syndrome can cause endothelial dysfunction. 

The Role of Monitoring Endothelial Function in Heart Attack and Stroke Prevention 

The maintaining healthy endothelium is the first defense against atherosclerosis. It serves as a physical barrier that protects against plaque build up. It is also a factory that manufactures many regulatory chemicals. One of them is Nitric Oxide which causes the arteries to dilate and increase blood flood. Vendys measures the temperature change caused by increased blood flow as an indicator of the health of the endothelium.  

Endothelial cells form the lining of all blood and lymphatic vessels within the vascular tree. The adult human body contains at least one trillion endothelial cells, which weigh more than 100 g and cover a surface area of more than 3000 square meters. They constitute a distributed organ that forms a dynamic interface with all other organs in the body.

The endothelium mediates vasomotor tone, regulates cellular and nutrient trafficking, maintains blood fluidity.

It contributes to the local balance between pro- and anti-inflammatory mediators as well as procoagulant and anticoagulant activity, participates in generation of new blood vessels, orchestrates organ development, participates in innate and acquired immunity and interacts with circulating blood cells. Each of these activities is dynamically and carefully regulated. 

The health of the endothelial is affected negatively by several modifiable risk factors such as high blood pressure, diabetes, smoking, obesity, physical inactivity and hypercholesterolemia.

Abnormal endothelial function fosters and accelerates the development of atherosclerosis. An improvement in endothelial function can protect us from such clinical events as heart attack and stroke.

Optimal medical therapy and healthy lifestyle can significantly improve endothelial function. The Vendys test helps track changes in endothelial function over time.

© Rolando L. deGoma MD  2018     www.deGomaMD.com     Capital Cardiology Associates     Princeton Physicians Organization