Arteriosclerosis and Atherosclerosis PDF

1/16/24, 10:19 PM Realizeit for Student Introduction Arteriosclerosis (hardening of the arteries) is the most common disease of the arteries. It is a diffuse process whereby the muscle fibers and the endothelial lining of the walls of small arteries and arterioles become thickened. Atherosclerosis...

1/16/24, 10:19 PM Realizeit for Student Introduction Arteriosclerosis (hardening of the arteries) is the most common disease of the arteries. It is a diffuse process whereby the muscle fibers and the endothelial lining of the walls of small arteries and arterioles become thickened. Atherosclerosis involves a different process, affecting the intima of large and medium-sized arteries. These changes consist of the accumulation of lipids, calcium, blood components, carbohydrates, and fibrous tissue on the intimal layer of the artery. These accumulations are referred to as atheromas or plaques. Although the pathologic processes of arteriosclerosis and atherosclerosis differ, rarely does one occur without the other, and the terms are often used interchangeably. Atherosclerosis is a generalized disease of the arteries, and when it is present in the extremities, it is usually present elsewhere in the body. Arteriosclerosis and Atherosclerosis Pathophysiology The most common direct results of atherosclerosis in arteries include stenosis (narrowing) of the lumen, obstruction by thrombosis, aneurysm, ulceration, and rupture. Its indirect results are malnutrition and the subsequent fibrosis of the organs that the sclerotic arteries supply with blood. All actively functioning tissue cells require an abundant supply of nutrients and oxygen and are sensitive to any reduction in the supply of these nutrients. If such reductions are severe and permanent, the cells undergo ischemic necrosis (death of cells due to deficient blood flow) and are replaced by fibrous tissues, which require much less blood flow. Atherosclerosis can develop in any part of the vascular system, but certain sites are more vulnerable, such as regions where arteries bifurcate or branch into smaller vessels, with males having more below-the-knee pathology than females (Jelani, Petrov, Martinez, et al., 2018). In the proximal lower extremity, these include the distal abdominal aorta, the common iliac arteries, the orifice of the superficial femoral and profunda femoris arteries, and the superficial femoral artery in the adductor canal, which https://herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zbfuwFjUs0mdxkPeVey4KH2F7i%2fH0LC0NH7inQLoUzK%2fM… 1/4 1/16/24, 10:19 PM Realizeit for Student is particularly narrow. Distal to the knee, atherosclerosis can occur anywhere along the course of the artery. Although many theories exist about the development of atherosclerosis, no single theory explains the pathogenesis completely; however, tenets of several theories are incorporated into the reaction-to-injury theory. According to this theory, vascular endothelial cell injury results from prolonged hemodynamic forces, such as shearing stresses and turbulent flow, irradiation, chemical exposure, or chronic hyperlipidemia. Injury to the endothelium increases the aggregation of platelets and monocytes at the site of the injury. Smooth muscle cells migrate and proliferate, allowing a matrix of collagen and elastic fibers to form (Norris, 2019). Atherosclerotic lesions are of two types: fatty streaks and fibrous plaque. •Fatty streaks are yellow and smooth, protrude slightly into the lumen of the artery, and are composed of lipids and elongated smooth muscle cells. These lesions have been found in the arteries of people of all ages, including infants. It is not clear whether fatty streaks predispose a person to the formation of fibrous plaques or whether they are reversible. They do not usually cause clinical symptoms. •Fibrous plaques are composed of smooth muscle cells, collagen fibers, plasma components, and lipids. They are white to white-yellow and protrude to various degrees into the arterial lumen, sometimes completely obstructing it. These plaques are found predominantly in the abdominal aorta and the coronary, popliteal, and internal carotid arteries, and they are believed to be progressive lesions. Gradual narrowing of the arterial lumen stimulates the development of collateral circulation. Collateral circulation arises from preexisting vessels that enlarge to reroute blood flow around a hemodynamically significant stenosis or occlusion. Collateral flow allows continued perfusion to the tissues, but it is often inadequate to meet increased metabolic demands, and ischemia results. Risk Factors Many risk factors are associated with atherosclerosis. Although it is not entirely clear whether modification of these risk factors prevents the development of cardiovascular disease, evidence indicates that it may slow the process. The use of nicotine products may be one of the most important risk factors in the development of atherosclerotic lesions. Nicotine in tobacco decreases blood flow to the extremities and increases heart rate and blood pressure by stimulating the sympathetic https://herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zbfuwFjUs0mdxkPeVey4KH2F7i%2fH0LC0NH7inQLoUzK%2fM… 2/4 1/16/24, 10:19 PM Realizeit for Student nervous system, causing vasoconstriction (Quintella Farah, Silva Rigoni, de Almeida Correia, et al., 2019). It also increases the risk of clot formation by increasing the aggregation of platelets. Carbon monoxide, a toxin produced by burning tobacco, combines more readily with hemoglobin than oxygen, depriving the tissues of oxygen. There is evidence that smoking decreases high-density lipoprotein (HDL; good cholesterol) levels and alters the ratios between HDL and low-density lipoprotein (LDL; bad cholesterol), HDL and triglycerides, and HDL and total cholesterol levels. The amount of tobacco used—inhaled in traditional or e-cigarette form, or chewed—is directly related to the extent of the disease, and cessation of any type of nicotine product use reduces the risk (Jelani et al., 2018). Diabetes increases the overall risk of peripheral artery disease (PAD) two- to fourfold, with amputation rates 5 to 10 times higher than in patients without diabetes. Patients with diabetes show an earlier onset and more rapid progression of PAD than patients without diabetes; furthermore, they also exhibit a different anatomic distribution of pathology, with a greater severity of disease in the profunda femoris and in all segments below the knee (Gerhard-Herman et al., 2016). How diabetes affects the onset and progression of atherosclerosis is multifactorial and includes incitation of inflammatory processes, derangement of various cell types within vessel walls, promotion of coagulation, and inhibition of fibrinolysis (Hazarika & Annex, 2017). Many other factors, such as obesity, stress, and lack of exercise, have been identified as contributing to the disease process. C-reactive protein (CRP) is a sensitive marker of cardiovascular inflammation, both systemically and locally. Slight increases in serum CRP levels are associated with an increased risk of damage in the vasculature, especially if these increases are accompanied by other risk factors, including increasing age, hypertension, hypercholesterolemia, obesity, elevated blood glucose levels, use of nicotine products, or a positive family history of cardiovascular disease (Hazarika & Annex, 2017). In some studies, hyperhomocysteinemia has been positively correlated with the risk of peripheral, cerebrovascular, and coronary artery disease as well as venous thromboembolism (VTE). Homocysteine is a protein that promotes coagulation by increasing factor V and factor XI activity while depressing protein C activation and increasing the binding of lipoprotein(a) in fibrin. These processes increase thrombin formation and the propensity for thrombosis. Folic acid and vitamin B12 have been reported to reduce serum homocysteine levels but there are no data demonstrating this therapy reduces adverse cardiovascular events. Thus, the use of B complex vitamins to https://herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zbfuwFjUs0mdxkPeVey4KH2F7i%2fH0LC0NH7inQLoUzK%2fM… 3/4 1/16/24, 10:19 PM Realizeit for Student reduce cardiovascular disease in patients with PAD is not recommended (GerhardHerman et al., 2016). https://herzing.realizeithome.com/RealizeitApp/Student.aspx?Token=lqf9HhURQ5RqpgqAkzH2zbfuwFjUs0mdxkPeVey4KH2F7i%2fH0LC0NH7inQLoUzK%2fM… 4/4