MAJOR FORMS OF CARDIOVASCULAR DISEASE
Although deaths from CVD have declined drastically over the past 60 years, it remains the leading cause of death in America. According to the National Center for Health Statistics, heart disease killed nearly 600,000 Americans in 2011. The financial burden of CVD, including the costs of medical treatments and lost productivity, exceeds $313 billion annually. Although the main forms of CVD are interrelated and have elements in common, we treat them separately here for the sake of clarity. Hypertension, which is both a major risk factor and a form of CVD, was described earlier in the chapter.
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Atherosclerosis is a form of arteriosclerosis, or thickening and hardening of the arteries. In atherosclerosis, arteries become narrowed by deposits of fat, cholesterol, and other substances. The process begins when endothelial cells (the cells lining the arteries) become damaged, most likely through a combination of factors such as smoking, high blood pressure, high insulin or glucose levels, and deposits of oxidized LDL particles. The body’s response to this damage results in inflammation and changes in the artery lining. Deposits, called plaques, accumulate on artery walls; the arteries lose their elasticity and their ability to expand and contract, restricting blood flow. Once narrowed by a plaque, an artery is vulnerable to blockage by blood clots. (See page T3-4 of the color transparency insert “Touring the Cardiorespiratory System” in Chapter 3.) The risk of life-threatening clots and heart attacks increases if the fibrous cap covering a plaque ruptures.
If the heart, brain, and/or other organs are deprived of blood and the oxygen it carries, the effects of atherosclerosis can be deadly. Coronary arteries, which supply the heart with blood, are particularly susceptible to plaque buildup, a condition called coronary heart disease (CHD), or coronary artery disease (CAD). The blockage of a coronary artery causes a heart attack. If a cerebral artery (leading to the brain) is blocked, the result is a stroke. The main risk factors for atherosclerosis are cigarette smoking, physical inactivity, high levels of blood cholesterol, high blood pressure, and diabetes.