Understanding How Plaque Build-Up Occurs
In this post, I’m going to address the presence of cholesterol in the area of plaque and explain, at least in part, the relationship between cholesterol and plaque and cardiovascular disease.
It is an important question - If cholesterol doesn't cause plaque, why is there cholesterol in plaque? What's the relationship?
WHAT CAUSES ARTERIAL PLAQUE BUILD-UP?
The presence of cholesterol in plaque is the result of damage to the artery wall and the subsequent repair process. Oxidation doesn't only affect the artery wall, but also anything that is in the area including lipoprotein and its lipids.
Anything that causes excessive oxidation to damage the artery wall (vegetable oil, cigarettes, iron, etc.) can also destabilize and damage cholesterol. Once cholesterol and lipoprotein are damaged this way, they become useless and even dangerous.
Part of the repair response includes the arrival of white blood cells; whose function is to remove damaged, harmful compounds and debris. The artery wall, and its collagen and other connective tissue components need to be replaced by new healthy components. The old material is removed bit by bit by white blood cells. The damaged lipid compounds, including oxidized cholesterol, are also removed by these white blood cells and these compounds are toxic to the white blood cells.
As a result, these white blood cells die and release their contents into the site of the plaque. When you look at plaque under a microscope you can see these white blood cells appear with white or yellow content and that is the oxidized cholesterol they “swallow” as they remove it from the area. They look as if they are filled with foam and this appearance lent them the name “foam cells”. As they die from their toxic oxidized cholesterol content, the spilled cholesterol contributes to plaque build-up and narrowing of the arteries.
It makes little difference how much cholesterol is circulating in the arteries What is important is whether that cholesterol gets oxidized or not. You could have higher than normal levels of cholesterol, but without oxidative damage it will never contribute t plaque build up. I have patients with very high cholesterol levels, whose arteries appeared perfectly healthy and normal upon undergoing imaging tests such as a carotid artery ultrasound scan.
Factors that may oxidize cholesterol and harm the artery wall include smoking, iron, environmental toxins, bacterial bi-products (endotoxins) and most commonly, polyunsaturated fatty acids from vegetable oil.
CORONARY THROMBOSIS AND HOW HEART ATTACKS OCCUR
The last thing I want to talk about how a heart attacks occur and the relationship to plaque formation.
A myocardial infarction (the inability to deliver oxygen to any given area of the heart), most commonly occurs when a coronary artery becomes occluded following the rupture of an atherosclerotic plaque, which then leads to the formation of a blood clot or coronary thrombosis.
Ruptured plaque material from a larger blood vessel travels to the coronary arteries, which tend to be smaller. The likelihood of a heart attack increases if the wall of the coronary artery is thickened by atherosclerosis, which causes this already narrower blood vessel to be further narrowed.
When this event occurs, the myocardium, meaning the muscle cells in the area which are normally supplied by that vessel, would become ischemic and hypoxic, meaning they will stop receiving oxygen and without sufficient oxygen, the tissue dies.
CORONARY OCCLUSION AND STRESS
The other thing that can happen is a raptured piece of plaque would travels through smaller vessels and trigger vasospasm. A coronary vasospasm is basically a nervous response of the affected artery in a away that results in the constriction of the muscles fibers that surround the artery. Even if the raptured piece of plaque isn’t large enough to completely block a smaller coronary artery, spasm or the constriction of the coronary artery can contribute to a complete occlusion that prevents blood from traveling any further, resulting in lack of oxygen delivery and therefore a heart attack. Extreme stress can also elicit spasm of the arteries and be a contributing factor in for a heart attack.