Ischemic heart disease (coronary artery disease) is the most common spectrum of heart disease.1-6 It develops gradually as the coronary arteries supplying blood to the heart become progressively blocked with atherosclerotic plaque, a combination of oxidized low-density lipoproteins (LDL), inflammatory cells (macrophages), smooth muscle cells, and debris1218 (see other chapters). Eventually, blood supply may become completely interrupted by plaque, or more commonly by a coronary thrombosis (blood clot) when plaque ruptures, precipitating a heart attack (myocar-dial infarction, MI).18 As ischemia continues for several minutes, the myocardium is deprived of oxygen and muscle cells may die, leading to permanent damage to heart tissue, heart failure, or sudden death. Other heart disorders include arrhythmias (dysfunction of the electrical conduction system of the heart); valve disorders; and congestive heart failure. The pain or discomfort associated with advanced ischemic heart disease is known as angina.
Stroke is a cerebrovascular accident, characterized by a reduction in blood supply to a region of the brain. This leads to a reduction of oxygen tension and of high-energy metabolites in an area of the brain. Previously held to be a disease of the elderly, cerebrovascular compromise is now recognized as affecting all age groups. There are two main types of stroke, namely ischemic (thrombotic) stroke and hem-orrhagic stroke.19 As the name implies, a thrombotic stroke occurs when there is a clot, embolus or other blockage, such as narrowing induced by atherosclerotic plaque, in a cerebral artery.19 This causes a sudden cessation of blood flow (ischemia) that is usually temporary, followed by dislodging of the clot and reestablishment of blood flow (reperfusion). As brain tissue is deprived of oxygen and nutrients, neuronal cells start to die, leading to long-term deficits in brain function (see Section 5.5). Approximately 80% of strokes are ischemic.19
Rupture of a blood vessel that is weakened (e.g., when an aneurysm occurs), brittle (after years of hypertension and atherosclerosis), or defective (when arteriovenous malformation is present) leads to hemorrhagic stroke.19 Within this category, differences exist. For example, a brain hemorrhage can be intracerebral (within the brain; intracranial hematoma) or subarachnoid (between the brain and the overlying skull and connective tissue layers), depending on the site of the ruptured blood vessel. Regardless of the site, the leaking of blood into and around the brain increases intracranial pressure, which compresses brain tissue. As well, the flow of blood to certain brain regions is disrupted, ultimately damaging the brain.19
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