If the coronary arteries that feed the heart muscle with blood containing oxygen and nutrients become partially blocked, the muscle becomes painful when used. The lack of blood to the heart muscle is called myocardial ischemia, and it is typified by characteristic ECG findings of ST-segment depression. (See the ECG in Figure 4.)
As far back as the time of the Caesars, pain in the legs due to obstruction of blood flow in arteries to the legs was labeled as intermittent claudication. The Emperor Claudius limped because of a painful leg, and the word claudication is derived from his name. Similarly, angina occurs because of a reduced blood supply.

B. Atheroma
After age 30 the coronary arteries become slowly obstruc¬ted by sludge consisting of cholesterol and smaller blood particles called platelets. The sludge forms a hardness, or plaque, which doctors call atheroma. These plaques bulge into the interior of the arteries, obstructing the free flow of blood (see Fig. 1 and the chapter Atherosclerosis). The word atheroma is derived from the Greek ‘‘athere’’ meaning porridge or gruel. When a plaque of atheroma is cut open, one can see a gelatinous, porridge-like material which contains cholesterol. Fortunately, this porridge-like fatty 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. A plaque of atheroma therefore consists of a central fatty core, covered by a fibrous cap (Fig. 1).

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