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Why can atherosclerotic plaques reduce blood flow through an artery?

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The role of coronary artery disease in heart attack — cardiovascular disease This micrograph shows a cross section of a coronary artery narrowed by an atherosclerotic plaque (purplish matter inside the artery). Most heart attacks are caused by the rupture of an atherosclerotic plaque, which triggers the formation of a clot that abruptly blocks blood flow to part of the heart muscle.

Atherosclerotic plaques reduce blood flow through an artery primarily by physically narrowing the vessel channel, known as the lumen.12

The process begins when the endothelium of an artery is injured, leading to the accumulation of cholesterol, lipids, immune cells, and cellular debris. These materials form an atheroma, or atherosclerotic plaque, which enlarges and thickens over time. As the plaque grows, it encroaches upon the space available for blood to travel, effectively reducing the luminal diameter.12

When this narrowing becomes severe—typically exceeding 70 percent of the vessel's diameter—the artery can no longer accommodate adequate blood flow, particularly during periods of physical stress. Furthermore, these plaques can trigger the formation of a thrombus (blood clot) or rupture, which can cause a sudden, catastrophic obstruction of the artery. By restricting the delivery of oxygen-rich blood to tissues, these plaques can lead to serious complications such as angina pectoris, myocardial infarction, or stroke.321