How does atherosclerosis occur?
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Scientists believe that an initial injury must occur to the cell wall lining an artery to kick things off. Then a continual insult must occur to allow for atherosclerosis to progress. The injury allows for monocytes to leave the blood and enter into the wall (See Atherosclerosis Figure). The injured cells lining the artery release chemicals that signal monocytes to come in. Platelets arriving on the scene to patch the artery wall also release chemicals. Some of the chemicals encourage the relocation of smooth muscle cells from the media to the intima. More and more LDLs also move through the injury opening. So what we have is a mixture of stuff arriving in the intima and in excess normal operations. |
The monocytes, which are soon transformed into insatiably hungry macrophages, begin to ingest the LDLs in the intima. LDL can become modified (oxidized LDLs) by free radicals from cigarette smoke, environmental pollutants, foods or produced in the body and macrophages find oxidized LDL most delicious. The ingestion of oxidized LDLs by macrophages gives them a foamy appearance when seen with a microscope and they are often referred to as foam cells. Furthermore, smooth muscle cells begin to release fibrous proteins into the area, and calcium-rich complexes also begin to accumulate. While all this is happening, new monocytes and LDLs continuously arrive on the scene from the blood and smooth muscle cells migrate from the media. So the process continues.
When does atherosclerosis begin?
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Although the medical complications of atherosclerosis (i.e., heart attack or stroke) occur suddenly, the disease really develops over a very long stretch of time (see Table below). Atherosclerosis is a chronic degenerative disease, which means that the inception of atherosclerosis may be established very early in life and progresses from there to a critical point. In fact, cadavers of children have shown evidence that the foundations of atherosclerosis may be noticeable as early as 10 to 12 years of age. Therefore, it should be realized that atherosclerosis is not a disease of old age but of a lifetime. It can take decades for the blockage to reach a critical point and blood flow to become insufficient or for a blood clot to become lodged in a partially blocked vessel. |
Many people atherosclerosis may be undetected as early warning signs of a heart attack have not been experienced. Therefore when the heart attack does occur it seems unexpected and happens suddenly and without warning. In fact about ½ of the people in the United States that die of heart disease can be characterized as sudden cardiac death. This means that early detection is very important!
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Chest pain (angina) |
