Atherosclerosis

Atherosclerosis is a chronic inflammatory disease that affects the walls of the arteries.

Arteries are the essential tubes that carry oxygen-rich blood throughout the body. In this condition, abnormalities known as lesions develop within the arterial walls. These lesions can eventually grow into buildups called atheromatous plaques. As these plaques accumulate, they cause the arterial walls to narrow. This narrowing restricts the flow of vital blood to different organs and tissues. Because it can lead to severe health crises, it is a major medical concern.

The process of plaque buildup is called atherogenesis. It is a slow process that develops over many years. It begins when low-density lipoprotein (LDL) particles enter the endothelium. The endothelium is the thin lining on the inside of the artery. Once inside the wall, these LDL particles become oxidized through biochemical reactions. This oxidation triggers an inflammatory response in the vessel.

White blood cells called monocytes are recruited to the site of this injury. They migrate into the sub-endothelial space, which is the area just beneath the lining. Once there, the monocytes differentiate into cells called macrophages.

These macrophages attempt to clean up the area by ingesting the oxidized cholesterol. However, this process leads to the formation of a complex plaque. This plaque is composed of fat, cholesterol, immune cells, and calcium.

As the plaque grows, the muscle cells of the blood vessel may stretch to accommodate the extra bulk. The endothelial lining often thickens in response to this pressure. While this thickening might slightly offset the narrowing of the lumen, it also causes the artery to stiffen. This makes the vessel less compliant, meaning it cannot stretch easily with every heartbeat.

Symptoms of atherosclerosis often do not appear for many decades. This is because the arteries can enlarge at plaque locations to maintain blood flow. Most people only realize they have the disease when a major event occurs. For example, a sudden rupture of a plaque can lead to a blood clot. This clot can cause a total blockage of the artery.

Such blockages can result in heart attacks, strokes, or kidney disorders. The specific symptoms depend entirely on which part of the body is being deprived of blood.

The impact of this disease is widespread and significant. It is the leading cause of death and disability in developed countries. Most people are affected by some degree of atherosclerosis by the age of 65. Historical studies have shown how early this process can begin. In an autopsy of 300 U.S. soldiers from the Korean War, 77.3 percent showed evidence of coronary arteriosclerosis. The average age of these men was only 22.1 years.

This shows that the disease can be present even in very young adults.

Different locations in the body produce different medical outcomes. If the coronary arteries narrow, a person may experience angina, which is chest pain. They might also feel shortness of breath, nausea, or palpitations.

If the carotid arteries, which supply the brain, are affected, it can lead to a stroke. Symptoms of a carotid blockage include difficulty speaking, blurred vision, or numbness. Narrowing in the renal arteries can lead to chronic kidney disease. Even the peripheral arteries in the arms and legs can cause pain and numbness if they become blocked.

Scientists are still working to understand the exact causes of this disease. It is believed to be multifactorial, meaning many different things contribute to it. Risk factors include high blood pressure, diabetes, and obesity. Smoking and an unhealthy diet are also major contributors. Some people also have a genetic predisposition that makes them more likely to develop the disease.

Some evidence even suggests that genetic mutations related to this disease may have occurred over two million years ago in our ancestors. This links the modern disease to very deep evolutionary history.