Ischemia happens when blood flow is reduced or stopped to a body part, leading to decreased oxygen supply to that part of the body. Types of ischemia get their names according to where they occur in the body. Anything disrupting blood flow can cause ischemia, but most cases are caused by a clot that either develops in the artery or travels to the artery from somewhere else in the body.
Global cerebral ischemia occurs when the entire brain is deprived of oxygen. It is not usually caused by a blockage but results from very low blood pressure. Sometimes, global cerebral ischemia is transient or temporary. Disruptions to the autonomic nervous system can cause it, and these affect blood pressure and heart rate. Structural problems and arrhythmias may also be responsible.
When the brain is deprived of oxygen for a longer period, it results in prolonged global ischemia, which causes permanent brain damage.
Focal brain ischemia affects a smaller, more specific area of the brain. The most common cause is obstruction due to a clot or embolism, which cuts off blood supply to the brain and causes an ischemic stroke. Often, this results from a clot traveling from the heart or a large artery, into the brain.
Symptoms of brain ischemia vary depending on the type. People with transient global cerebral ischemia may faint. Prolonged global cerebral ischemia typically results in a coma. Focal cerebral ischemia affects only parts of the brain, so it may be difficult to pick up on symptoms.
People experiencing an ischemic stroke may experience weakness, sensory loss, visual defects, or lack of muscle control.
The only treatment for brain ischemia caused by blood clots is to remove the clot. The gold-standard treatment for ischemic stroke is r-tPA. This IV medication dissolves the clot and improves blood flow, but must be administered within three hours of the start of symptoms.
When a larger vessel is blocked, doctors may mechanically remove it by inserting a catheter with a stent through an artery in the groin and into the brain. The stent opens the blood vessel, so the clot can be removed and the normal blood flow is restored.
Ischemic cardiomyopathy happens when the blood supply to the heart is affected. The most common cause of this type of ischemia is coronary artery disease. Plaques build up in the blood vessels supplying the heart, depriving it of the nutrients and oxygen it needs to work effectively. Initially, the damage is reversible, but prolonged ischemia leads to decreased heart function, arrhythmias, and eventually congestive heart failure.
Symptoms of ischemic cardiomyopathy vary depending on the severity of the damage and can include shortness of breath, swelling of the feet and legs, and fatigue occurring either with exercise or at rest. People with this condition may experience weight gain and congestion from fluid retention, and abnormal heart rhythms may cause dizziness or fainting without a clear reason. Chest pain and chest discomfort are also symptoms of ischemic cardiomyopathy.
To treat ischemic cardiomyopathy, doctors focus on treating the coronary artery disease that caused it as well as reducing symptoms and improving heart function. Medications like beta-blockers, diuretics, and blood thinners can improve heart function, and a low sodium diet is often necessary once the person begins experiencing fatigue or shortness of breath. The doctor will advise whether it is safe to exercise and what activities are appropriate.
Some people may need a pacemaker or internal defibrillator to maintain a regular heart rhythm. Surgery may also be beneficial to insert stents or bypass any significant blockages.
There are two types of bowel ischemia. The most common is colon ischemia, which can be caused by dangerously low blood pressure, blood clots, twisting of the colon, hernias, scar tissue, or tumors.
Mesenteric ischemia affects the small bowel — the acute form has a rapid onset and is usually caused by a clot in the superior mesenteric artery, which supplies blood to the intestine. Chronic mesenteric ischemia happens when fat deposits build up in the vessels supplying blood to the intestines. Symptoms may not develop until two of the three main arteries supplying the intestines are obstructed.
Symptoms of bowel ischemia can appear suddenly or slowly develop over time. Signs of acute onset include sudden, sometimes severe, abdominal pain, abdominal distention and tenderness, frequent bowel movements, urgency, and blood in the stool.
Symptoms of chronic bowel ischemia include fullness after eating that lasts as long as three hours, worsening abdominal pain, unintended weight loss, fear of eating, nausea, bloating, and diarrhea.
Treatment depends on the type of bowel ischemia. Acute mesenteric ischemia is a medical emergency. It has a high mortality rate, and treatment involves mechanical removal of the clot. Many people with this condition also require a bowel resection to remove damaged tissue. Colon ischemia is treated by locating and treating the underlying cause. Mild cases are treated conservatively, while more severe cases may require antibiotics, a colonoscopy to assess circulation, and surgery.
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