Skip to content
Explore atlas
PH-CV01

Atherosclerosis

How lipid and inflammation build a plaque in the wall of an artery, why a fixed narrowing causes pain on exertion, and why a ruptured plaque blocks the artery suddenly.

By the end, you can

  • Describe the normal artery wall and the endothelium’s role in keeping blood flowing.
  • Explain how endothelial dysfunction, LDL and macrophages form a fatty streak and then a fibrous plaque.
  • Relate a fixed stenosis to symptoms that appear on exertion, such as angina and claudication.
  • Explain how plaque rupture triggers thrombosis and an acute event such as a heart attack or stroke.
  • Distinguish a stable plaque from a vulnerable plaque.
  • Recognise the classic appearances, classifications and tests of atherosclerosis, and explain how lipid-lowering, antiplatelet and revascularisation treatments act on its mechanism.

What it is

Atherosclerosis is a chronic inflammatory disease of the intima of large and medium-sized arteries, in which lipid, immune cells, smooth muscle and fibrous tissue build up into plaques (atheromas). It is one form of arteriosclerosis (hardening of arteries); arteriolosclerosis of small arterioles, seen in hypertension and diabetes, is a different process.

3 types to tell apart
Stable plaque
A thick fibrous cap over a small lipid core. It narrows the artery gradually and causes symptoms on exertion.
Vulnerable plaque
A thin, inflamed cap over a large lipid core (a thin-cap fibroatheroma). It may not narrow the artery much, but it can rupture and cause sudden thrombosis.
Rupture and erosion
Thrombosis usually follows a tear in the cap (rupture). It can also form on an intact plaque whose surface endothelium has been lost (erosion).

Normal function

A healthy artery wall

A muscular artery has three coats. The innermost, the , is a single layer of endothelium on a thin layer of connective tissue. The separates it from the of circular smooth muscle, and the of connective tissue carries the wall’s own small vessels, the .

Healthy endothelium does much more than line the vessel. It releases nitric oxide, which relaxes the smooth muscle and widens the artery. It resists clotting and stops white cells sticking. It also controls which molecules can enter the wall.

The width of the lumen matters greatly for flow. In a simple model of flow through a tube, resistance rises with the fourth power of narrowing: halving the radius cuts flow to about a sixteenth at the same pressure. Real arteries partly compensate by widening the vessels downstream.

Point to it on the model