Ischemia is the lack of delivery of oxygen to a major organ, most often affecting the heart or the brain. Blood flow is either blocked, or the blood flowing to the organ has an extremely low oxygen saturation. Since all of the body’s tissues need oxygen to maintain function, ischemia can result in shut down of an organ or significant damage to the organ.

Several conditions can cause ischemia, including the following:
• Sickle Cell Anemia
• Compression of blood vessels
• Ventricular Tachycardia
• Plaque build-up in arteries (atherosclerosis)
• Blood clots
• Extremely low blood pressure as caused by heart attack
• Congenital Heart Defects

Sickle Cell Anemia can cause ischemia because irregularly or sickle shaped blood cells can clot more easily, blocking oxygen rich blood to either the heart, lungs or brain. Rarely, a clot can block passage of oxygen to other organs like the liver, creating significant damage. Most with Sickle Cell Anemia take anti-clotting medications to prevent ischemia.

Blood vessels can be compressed from the outside by growths. Tumors can press on major arteries blocking oxygen pathways, resulting in ischemia. Where other factors do not exist, ischemic episodes may indicate either the presence of cancer or large benign tumors.

Ventricular Tachycardia is a series of sudden irregular heartbeats that can cause the heart to function incorrectly, or in the most severe cases to stop completely. Resultant complications can include ischemia, since significant arrhythmias causing irregular heart function may also inhibit oxygen flow. In cardiac death as a result of ventricular tachycardia, the heart stops completely, depriving the entire body of oxygen. Though a person can be revived with the use of a defibrillator, length of oxygen deprivation may have caused damage to major organs.

Atherosclerosis is the narrowing of arteries caused by the build-up of plaque. This is frequently seen in the elderly, and can usually be corrected. However, ischemia may first present when an artery becomes so completely blocked that blood cannot get to the brain or lungs. As well, narrow passageways make it easier for blood to clot and completely block the arteries.

Blood clots can be caused by people having a high platelet count, by surgical procedures, or in those taking an excess of blood clotting agents. As well, some blood clots can form in the legs of those who are inactive. In very rare cases, blood clots can form in the legs during long airplane flights, causing almost immediate ischemia. Often blood clots are too small to block veins and arteries, but occasionally a large clot can block blood flow to a major organ, creating great damage.

One suffering a heart attack usually exhibits extremely low blood pressure, which represents inadequate oxygenation of tissues. Untreated and undiagnosed heart attacks can slow blood flow enough that clots are formed creating ischemic conditions. Those who have had repeated heart attacks may be at greater risk for ischemia.

Those with congenital heart defects are also at increased risk for ischemia due to clotting, both before and after reparative surgery. Some with congenital heart defects are at immediate risk for ischemia at birth, due to lack of appropriate artery formation, artery connection or missing arteries.

Those who are prone to heart attacks or blood clots are given appropriate medications to reduce risk of ischemia. Plaque build up may be controlled with medications, and diets, which reduce cholesterol. Episodes of ventricular tachycardia may be treated with either rhythm controlling medication, or with an implanted pacemaker or defibrillator. When possible, tumors inhibiting blood flow are removed. As well, surgical correction of congenital defects can create normal blood flow patterns. All of the above help reduce the risk of ischemia in predisposed patients. Prevention is ultimately better than attempting to alleviate the effects caused by an ischemic attack.