What is Artherosclerosis?

Atherosclerosis is a disease of the artery wall characterized by the accumulation of lipids and various cells which leads to the formation of atherosclerotic plaques. It affects primarily the coronary arteries (arteries that carry blood to the heart, arranged in a crown-like shape around the heart), the aorta, the arteries of the lower extremities, and the arteries that provide blood to the brain.

The lining of the arteries is coated with a layer of cells called the endothelium, which blood components normally glide across. An atherosclerotic plaque begins to form when lipids (cholesterol-rich LDL lipoproteins) cross the endothelium and accumulate in the sub-endothelial layer. The penetration of lipids is a complex process caused by a dysfunction in the endothelium which, according to some hypotheses, could be triggered by infectious agents.

White blood cells, or monocytes, also enter the endothelium, where they become macrophages that accumulate LDL lipids and are transformed into foam cells.

Whether or not the accumulation of lipids described above is the triggering factor in plaque production, the formation and development of the plaque constitutes an inflammatory process involving white blood cells (monocytes as well as lymphocytes) and arterial cells (endothelial and muscle cells), with the production of cytokines and growth factors. This leads to remodeling of the arterial wall and the gradual obstruction of blood flow.

In this schematic representation, the atherosclerotic plaque is composed of a fatty core separated from the lumen by fibrillar collagen and numerous cells (arterial smooth muscle cells, monocytes, and lymphocytes).

The growth of an atherosclerotic plaque may partially block an artery or slow the flow of blood, causing ischemia in the corresponding organ. Atherosclerosis of the coronary arteries may cause angina with intense pain (angina) caused by the lack of blood to the heart muscle during physical effort (ischemia).

Cardiovascular events are caused by the rupture of an atherosclerotic plaque, an event that is still poorly understood and in which infectious agents may be implicated. Most often plaque disruption goes unnoticed, but the "clot" (thrombus) that forms at the rupture site, as is true for any blood vessel lesion, may completely block blood circulation. Depending on where it occurs, the rupture may cause limb ischemia, myocardial infarction, or a cerebrovascular event.