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a local deficiency of blood; insufficient blood in an organ or tissue because of the narrowing or complete occlusion of the lumen of an afferent artery.
Transitory ischemia (like hyperemia) may result from physiological regulation of the blood supply, such as in reflex spasm of an artery caused by a mental factor (fright); the influence of pain, cold, chemical substances (epinephrine, ergotin), and biological stimuli (bacteria, toxins); the obstruction of an artery by a thrombus or embolus; constriction of the lumen of a blood vessel in connection with an atherosclerotic or inflammatory process in the wall; or compression of an artery by a tumor, scar, or foreign body. The aftereffects of ischemia depend on the degree of disruption of the blood flow, the rate of development and duration of the ischemia, the sensitivity of the tissue to oxygen deficiency, and the general condition of the body. Ischemia may end in complete restoration of the structure and function of the affected organ or tissue, but it also may lead to necrosis (infarct). The central nervous system and heart muscle are particularly sensitive to ischemia.
N. R. PALEEV