Thrombosis
Thrombosis occurs when thrombi occlude vessels in the body. A thrombus, or a blood clot, is a mobilized mass of blood cells that circulates within the body. Thrombi can occlude veins (venous thrombosis) or arteries (arterial thrombosis). The etiology of thrombosis is described by Virchows Triad, which includes hemostasis, vascular wall damage, and hypercoagulability. Arterial thromboses significantly narrow or completely block arterial blood flow and oxygen delivery to tissues. Atherosclerosis
In atherosclerosis, the inner endothelial layer of arteries is stiffened by the deposition of an atheromatous plaque. Atheromatous plaques, also called atherosclerotic plaques, are made of fats and lipid-laden macrophages. Plaque deposition both physically narrows an artery and impairs the function of endothelial cells, potentiating their production of vasoconstrictive chemicals to constrict the arterial lumen. This leads to turbulent blood flow in the arteries, affecting oxygen supply to tissues downstream. Diseases of arterial occlusion
The pathophysiology of diseases of arterial occlusion depends on the type of occlusion, the severity of blockage, and the location of the occluded artery. Common diseases of arterial occlusion include Coronary Artery Disease, Peripheral Artery Disease, and Pulmonary Embolism. Coronary Artery Disease
Coronary Artery Disease (CAD) results from the stenosis of coronary arteries by an atherosclerotic plaque. The coronary arteries perfuse the cardiomyocytes located within the myocardium. Cardiomyocytes require constant perfusion to aid the pumping of the heart. In CAD, atheromatous plaque formation in a coronary artery limits oxygen supply to cardiomyocytes, impairing heart contractility. CAD severity varies based on the extent of coronary artery occlusion.
At 75% luminal narrowing, patients experience symptoms associated with limited perfusion of cardiomyocytes, especially under strenuous conditions. Under physical exertion, CAD induces chest pain, termed stable angina. Stable angina may deteriorate into unstable angina, marking the initiation of Acute Coronary Syndrome, which may further deteriorate into a myocardial infarction. Risk factors for CAD include smoking, high cholesterol, obesity, and family history of CAD. Primarily, the accumulation of cholesterol in the bloodstream from high-fat diets lead to atherosclerotic occlusion and its clinical consequences. Therefore, preventative measures for CAD mainly involve diet changes. A diet low in saturated and trans fats with an abundance of vegetables, fruits, and grains may lower the incidence of CAD. Peripheral Artery Disease
Peripheral artery disease (PAD), or limb ischemia, affects the femoral, popliteal, or iliac arteries. PAD is caused by atherosclerotic plaques that occlude blood flow to extremities. Once blood flow is impeded, ischemic muscle cells switch from aerobic to anaerobic metabolism to cope with oxygen scarcity. Anaerobic metabolism, however, is energy-inefficient, lowering the concentration of the intracellular energy molecule, ATP, within muscles. ATP depletion leads to a leakage of calcium into muscle cells, disrupting various muscular components and eventually causing muscle fiber necrosis.Risk factors for PAD include old age, smoking, hypertension, and high cholesterol, with smoking being the greatest contributing factor. This is because tobacco smoke contains potent chemicals that severely increase the occurrence of PAD. Thus, primary prevention of PAD is achieved with smoking cessation.