What is arterial plaque?

Causes and Symptoms

Arterial plaques are caused by a buildup of cholesterol
and cell debris within arterial walls. This process occurs over a period of decades, starting at local sites of arterial inflammation. Low-density lipoproteins carrying cholesterol (LDL-C) that infiltrate these sites are highly susceptible to oxidation, which activates another inflammatory response that summons macrophages (part of the immune system). The macrophages engulf the oxidized LDL-C and accumulate as bloated foam cells along with some other cells to become a fatty streak. A tug-of-war ensues in which cholesterol continues to accumulate while other processes remove it. When too much cholesterol accumulates, a scablike cap is formed, while other processes slowly calcify the plaque from the bottom up. This strategy works well as long as the cap does not crack; a cracked cap leaks debris into the artery, which triggers thrombosis (clotting). Blockage of a large coronary artery causes a heart attack; blockage of arteries feeding the brain causes a stroke. Clots that are not fully occlusive get degraded, but repeated rounds of plaque rupturing and recapping eventually cause stenosis
(narrowing of the artery) and ischemia
(oxygen starvation).

Treatment and Therapy

Treatment begins with lifestyle changes—exercising, managing stress, stopping smoking, lowering blood pressure, eating more fruits and vegetables. The next step is reducing high levels of LDL-C using statins, which also provide antioxidant, anti-inflammatory, and plaque-stabilizing benefits. Bile acid sequestrants and cholesterol absorption inhibitors are sometimes used as well. Fibrates and niacin are used to counteract LDL-C by boosting HDL-C, the high-density lipoprotein or “good” cholesterol. High blood pressure is typically treated using diuretics, beta blockers, or angiotensin-converting enzyme (ACE) inhibitors. Thrombosis risk is reduced using low-dose aspirin or drugs such as warfarin, clopidogrel, and prasugrel. Stenosis can be treated using nitroglycerin, ranolazine, and calcium-channel inhibitors to help arteries dilate. A common surgical procedure is to physically open the artery using a catheter, often done in conjunction with implanting a stent to keep the artery propped open. Surgery can also be used to scrape out arteries or replace them.

Perspective and Prospects

Once plaques reach their later stages of development, they are extremely difficult, if not impossible, to remove. Prospects are best when lifestyle changes are initiated early in adulthood. Blood tests for assessing risk factors are invaluable; the most useful ones measure fasting levels of glucose, total cholesterol, LDL-C, HDL-C, triglycerides, homocysteine, and C-reactive protein (a marker of inflammation). Monitoring and controlling blood pressure is also vitally important.

Bibliography

Crowley, Leonard V. An Introduction to Human Disease, Pathology, and Pathophysiology Correlations. 9th ed. Boston: Jones and Bartlett, 2013.

Mittal, Satish. Coronary Heart Disease in Clinical Practice. London: Springer, 2005.

Rosenblum, Laurie. "Atherosclerosis." Health Library, May 8, 2013.