– A disorder that impedes the bloodflow in the arteries serving the myocardium of the heart.
Causes and Incidence
The primary causes of coronary artery disease (CAD) are arteriosclerotic and atherosclerotic processes, which narrow and occlude the vessel lumen and thicken the arterial walls. Risk factors associated with the development of CAD include underlying disease (e.g., hypertension or diabetes); use of tobacco products; familial hyperlipidemia, high-fat diet; sedentary life-style; stress; estrogen use in women under 50 years of age; and obesity.
Vascular disease (CAD and CVA) is the leading cause of death in the United States. The incidence of CAD increases with age, and men seem more susceptible than women, particularly premenopausal women. The death rate among white men 55 to 64 years of age is about 1 in 100. CAD is much more prevalent in Western societies than in other areas of the world.
The exact pathologic mechanisms that induce atherosclerosis are not well understood. Current hypotheses are (1) the lipid hypothesis, in which an elevation of plasma low-density lipoprotein penetrates the arterial wall and causes a lipid buildup in the smooth muscle cells, and (2) the endothelial injury hypothesis, which suggests that a mechanical or chemical injury to the endothelial barrier sets up a tissue response, with platelet adhesion and aggregation. In either case, atherosclerosis is marked by changes in and thickening of the intimal lining of the arterial vessel. Lipids, smooth muscle cells, and connective tissue form a plaquelike substance on the lining. This process is slow and may occur over a lifetime. Arteriosclerosis causes hypertrophy and subintimal fibrosis, resulting in intimal thickening and loss of elasticity of the vessel wall, which widens the pulse pressure and increases the systolic pressure. This loss of elasticity is reinforced by atherosclerotic processes. Arterial lumens become increasingly narrow and may become obstructed, causing ischemia of the myocardium. The plaque may harden, calcify, and undergo fissure or rupture, simulating a thrombosis or embolus rapidly occluding a lumen.
CAD is asymptomatic until myocardial ischemia occurs. The two major manifestations of ischemia are chest pain (angina) and myocardial infarction. See Angina and Myocardial Infarction for diagnosis and treatment options.