atherosclerotic plaque

If atherosclerosis is the process, the plaque is the lump it produces — a raised, fatty bump growing into the channel of the artery, a bit like a blister on the inside of a hose.

A typical plaque has two key parts: a soft lipid core (cholesterol, debris and foam cells) and a fibrous cap of collagen and smooth-muscle cells that covers it and keeps it sealed off from the bloodstream. A thick, sturdy cap makes a stable plaque that mainly narrows flow. A thin, inflamed cap over a large lipid core makes a vulnerable plaque, prone to cracking.

Importantly, the plaques most likely to cause a heart attack are often not the largest. A modest plaque with a fragile cap can rupture and trigger a sudden clot, whereas a large but stable plaque may only cause predictable angina. This is why imaging the degree of narrowing tells only part of the story, and why plaque-stabilizing treatments such as statins matter even when narrowing seems mild.

Calcium often deposits in older plaques; coronary calcium scoring uses this to estimate overall plaque burden, though calcified plaque is generally more stable than soft, lipid-rich plaque.