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Ischemia in the heart and brain often causes no symptoms, and is sometimes referred to as “silent ischemia,” and the first sign may be an unexpected heart attack or stroke. When signs and symptoms of ischemia do occur, they depend on where it is in the body.
Ischemia is a vascular disease involving an interruption in the arterial blood supply to a tissue, organ, or extremity that, if untreated, can lead to tissue death. It can be caused by embolism, thrombosis of an atherosclerotic artery, or trauma.
Ischemia is almost always caused by blockage of an artery, usually due to atherosclerotic plaque. Myocardial ischemia is also caused by blood clots (which tend to form on plaque), artery spasms or contractions, or any of these factors combined.
It was Rudolf Virchow (1821-1902) who first used the term [ischemia] to denote a local reduction in the flow of blood. Today the term ischemia means "localized reduction in the flow of blood to an organ or region of an organ". Ischemia occurs when there is a stenosis or stricture of an artery.
Ischemia happens because something is keeping blood from reaching the tissues the blocked artery supplies. “Global ischemia” can also happen if your entire body is exposed to low blood pressure or low oxygen levels for a prolonged period. Ischemia causes include: Atherosclerosis. Blood clots. Abdominal hernia that becomes “strangulated.”
Ischemia and Hypoxia. Ischemia is insufficient blood flow to provide adequate oxygenation. This leads to tissue hypoxia (reduced oxygen) or anoxia (absence of oxygen). Ischemia results in hypoxia; however, hypoxia can occur with normal (or elevated) blood flow if, for example, the oxygen content of the arterial blood is decreased by anemia.
Ischemia is defined as a decrease in blood flow below the level necessary to sustain normal cell structure and function. Ischemia can be global, as in cardiac arrest or severe oligemia as may be seen with intracranial hypertension, or focal as in occlusion of an intracranial vessel by embolism or thrombus.
