The word atheroma is derived from the Greek ‘‘athere’’ meaning porridge or gruel. When a plaque of atheroma is cut open one sees a gelatinous, porridge-like material which contains globules of cholesterol fat, neutral fat, saturated sterols, protein granules, crystals of cholesterol, fatty acids, calcium, and other cells. The amount of calcium in the lesion (calcification) is extremely variable. Fortunately, the porridge-like material does not touch the blood that flows through the artery, because nature covers the fatty material with a protective hard layer of cells called fibrous tissue. The atheromatous material forms a plaque, an opaque yellowish-white patch of thickening, that juts into the lumen of the artery. An atheromatous plaque therefore consists of a central fatty core that has a variable amount of lipids and calcium covered by a fibrous cap. Because the cap is hard and the medical word for hardness is ‘‘sclerosis,’’ the disease is commonly called atherosclerosis. The fibrous cap, however, may be quite thin and fragile and prone to fracture and rupture or show erosion in some individuals. The exposed material is highly thrombogenic. Figure 2 gives a simplified representation of an atheromatous plaque and the subsequent rupture and blood clot that completely obstructs the artery.

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