Atherosclerosis Pathogenesis

Atherosclerosis is a chronic disease of the arterial wall in which lipids, inflammatory cells, and extracellular matrix accumulate to form plaques (atheromas) that narrow the lumen and can rupture. Its pathogenesis is the sequence of events — from endothelial dysfunction and lipoprotein retention to inflammation, plaque growth, and instability — that underlies coronary artery disease and most ischemic cardiovascular events.

Definition

Atherosclerosis is a progressive inflammatory and lipid-driven disease of medium and large arteries characterized by intimal accumulation of cholesterol-laden cells and matrix, forming plaques that narrow the lumen and may rupture or erode to trigger thrombosis.

Scope

This topic covers the biological mechanisms by which atherosclerotic plaques form, grow, and become unstable, with emphasis on the endothelium, lipoprotein retention, and the inflammatory response. It is the mechanistic foundation for the coronary artery disease area and does not address screening or treatment of individuals.

Core questions

• How do endothelial dysfunction and lipoprotein retention initiate plaque formation?
• What is the role of inflammation and the immune system in plaque progression?
• What makes a plaque vulnerable to rupture or erosion?
• How does plaque biology connect to the acute coronary syndromes?

Key concepts

• Endothelial dysfunction
• Lipoprotein retention and modification
• Foam cells
• Fatty streak
• Fibrous cap and necrotic core
• Vulnerable (rupture-prone) plaque
• Plaque erosion

Key theories

Response-to-retention / inflammatory hypothesis

Atherogenesis begins when apolipoprotein-B-containing lipoproteins are retained in the subendothelial intima and modified, provoking an inflammatory response in which monocyte-derived macrophages take up lipid to become foam cells, sustaining a chronic immune-inflammatory lesion rather than a passive lipid deposit.

Endothelial dysfunction as an initiating step

Loss of normal endothelial homeostasis — favored by disturbed flow at arterial branch points and by risk factors — increases permeability and adhesion-molecule expression, permitting lipoprotein entry and leukocyte recruitment that seed plaque formation.

Mechanisms

Atherogenesis is initiated where the endothelium becomes dysfunctional, particularly at sites of disturbed blood flow, increasing permeability to apolipoprotein-B lipoproteins and expression of leukocyte adhesion molecules (Gimbrone, 2016). Retained lipoproteins are oxidatively modified and taken up by recruited monocyte-derived macrophages, which become lipid-laden foam cells and form the earliest visible lesion, the fatty streak (Libby, 2002). Sustained inflammation, smooth-muscle cell migration, and matrix synthesis build a fibrous cap over a lipid-rich necrotic core; thinning of this cap and ongoing inflammation produce a vulnerable plaque prone to rupture, while superficial erosion can also expose thrombogenic surfaces, linking plaque biology to acute coronary events (Hansson, 2005; Libby, 2011).

Clinical relevance

Because coronary atherosclerosis is the substrate for most myocardial ischemia and infarction, its pathogenesis explains why risk factors such as dyslipidemia and inflammation matter and why plaque stability — not just stenosis severity — governs acute risk (Libby, 2019). This entry describes mechanisms to support evidence appraisal and is not guidance for managing any patient.

Epidemiology

Atherosclerosis underlies the majority of ischemic cardiovascular disease, the leading cause of death globally; its prevalence rises with age and with the burden of cardiovascular risk factors, though epidemiologic detail is covered in the parent area rather than here.

Evidence & guidelines

The inflammatory model of atherogenesis is supported by extensive experimental and translational research summarized in major reviews (Libby, 2011; Libby, 2019); clinical management of the resulting disease is addressed in cardiovascular-prevention and coronary-syndrome guidelines rather than in this mechanistic entry.

History

Nineteenth- and early twentieth-century pathology framed atherosclerosis largely as passive lipid encrustation. From the late twentieth century, work synthesized by Libby (2002) and Hansson (2005) reframed it as a chronic inflammatory and immune disease, and Gimbrone (2016) emphasized the endothelium and hemodynamics as initiating factors, a shift that continues to shape research and therapy (Libby, 2011).

Debates

Plaque rupture versus plaque erosion as the cause of acute events

Classic models emphasize rupture of a thin-capped, lipid-rich plaque, but a substantial fraction of coronary thromboses arise from superficial erosion of less inflamed plaques, and the relative contribution and distinct biology of erosion remain active questions.

Key figures

• Peter Libby
• Göran K. Hansson
• Michael A. Gimbrone

Seminal works

• libby-2002
• hansson-2005
• gimbrone-2016

Frequently asked questions

Is atherosclerosis just cholesterol building up in arteries?

Cholesterol-carrying lipoproteins are central, but the disease is now understood as a chronic inflammatory process: retained and modified lipoproteins provoke an immune response, and inflammation drives plaque growth and instability, not just passive lipid deposition.

Why can a smaller plaque be more dangerous than a larger one?

Acute coronary events depend more on plaque stability than on how much the plaque narrows the artery. A modest plaque with a thin, inflamed fibrous cap can rupture and trigger thrombosis, whereas a larger but stable plaque may not.