What Is Arterial Plaque, How Does it Form, and Why?

Atherosclerosis is a complex subject under continuous study by cardiology researchers. Why do humans get plaque? What is plaque? What is it made of? Why does plaque form in some areas and not others? The answers to these questions may surprise you. Our understanding of atherosclerosis is still evolving, and new risk factors continue to emerge.

Atherosclerosis (arterial plaque) results from the process of atherogenesis,[1] and unchecked atherogenesis often results in a heart attack. Arteriosclerosis is a similar-sounding term but refers to hardening (and loss of elasticity) of the arteries. It causes high blood pressure. In the most basic terms, plaque is the body’s response to injury at the artery wall. We used to call the plaque in arteries a “callus” analogous to the thickening of the skin in response to mechanical friction and pressure. This is one reason it is imperative to stay up to date if you are a doctor interested in preventive cardiology or if you are a patient keen on avoiding a heart attack.

Injury comes in two types: mechanical and chemical. Mechanical injury includes arterial stretching caused by the effects of blood pressure on the artery wall and shear stress caused by the frictional forces of passing blood cells over the inner lining of an artery over a lifetime, plus the stretching of the vessels with each pulse. Chemical injury includes factors, such as oxidative stress (not enough antioxidants or too much oxidative stress), dietary deficiencies, hormone imbalances, smoking, pollution, too much (or the wrong kind of) cholesterol, immune system dysfunction, and lack of nitric oxide.

In coronary artery disease (CAD), coronary arteries (the arteries that supply the heart) can become narrow with plaque, or the plaque itself can rupture. If a clot forms in a coronary vessel, it could block blood flow and lead to a myocardial infarction, or heart attack. The most common cause of a clot in a coronary vessel is a plaque rupture. The rupture attracts platelets and other clotting factors and causes a clot to form. We call this a thrombus. When the heart muscle does not get enough blood, part of it can die. So, both heart attacks and strokes are mediated by blood clots.

[1] Atherogenesis is the process of plaque formation. Atheroscleosis is the disease that arises form it.