Correlation 3: Acute myocardial infarctionNote in the picture above that the normal pattern of cross striations in the muscle fibers is lost, replaced by irregular contraction bands, and the central nuclei are gone because the myocardial fibers are dying from lack of a normal blood supply. The normal myocardial fibers are well supplied with blood from a rich vascular network of coronary arteries. The process of atherosclerosis leads to narrowing of these arteries. When there is an area of narrowing that is severe, then the blood supply to the myocardium is insufficient to maintain the cells. This leads to the death of the cells. The death of cells in a localized area supplied by an artery that cannot carry sufficient blood is called an infarct. In the case of the heart, this event is often sudden--a heart attack--and the patient has chest pain. The infarct can disrupt the normal flow of electrical impulses in the heart, leading to irregular contractions of the cardiac muscle and loss of the normal cardiac rhythm (an arrhythmia). If enough myocardium dies, then the heart cannot pump sufficient blood to maintain life. |
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