Ischemia is a condition in which insufficient blood flow to an organ in the body is often caused by atherosclerotic plaque in an artery supplying that organ . An organ prone to ischemia is called ischemic.
Because the ischemic organ does not receive all the oxygen and nutrients it needs, ischemia usually causes the affected organ to malfunction and often causes symptoms. If ischemia becomes severe enough or persists long enough, cells in the affected organ can begin to die. The death of all or part of an ischemic organ is called a heart attack.
Common examples of ischemia include:
- Cardiac ischemia
- Cerebral ischemia
- Intestinal ischemia
- Limb ischemia
Cardiac ischemia, also called myocardial ischemia, is most commonly caused by atherosclerotic plaques in the coronary arteries , the arteries that supply the heart muscle. However, cardiac ischemia can also be the result of other conditions, such as coronary artery spasm, cardiac syndrome X (also called coronary microvascular disease), or congenital anomalies of the coronary arteries .
"Typical" angina is a symptom of chest (or upper body) discomfort caused by cardiac ischemia caused by exercise or stress. Symptoms generally resolve with rest or relaxation.
Brain tissue is metabolically very active and the brain receives 20% of the blood pumped by the heart to function properly. Also , unlike many other organs, the brain does not have its own energy reserves and is completely dependent on continuous blood flow to do its work. Consequently, brain tissue quickly becomes ischemic if blood flow is interrupted, and if blood flow is not quickly restored, brain death rapidly occurs . The death of brain tissue is called a stroke .
Sometimes blood flow to part of the brain is cut off long enough to cause symptoms of cerebral ischemia, but not long enough to cause a true stroke. This condition is called a "transient ischemic attack" (TIA). A TIA can duplicate any of the many variations in stroke symptoms, except that the symptoms disappear within a few hours. TIAs are important not only because they are alarming in and of themselves, but also because they are often followed by a complete stroke. Therefore, TIA always requires immediate medical attention.
Intestinal ischemia (also called mesenteric ischemia) occurs when there is a disorder of the blood vessels that supply blood to the intestine.
Chronic intestinal ischemia, which is usually caused by atherosclerosis of the intestinal arteries, often causes recurrent symptoms after eating, as the intestines try to perform their digestive work under conditions of insufficient blood supply. Intestinal ischemia most often causes abdominal pain (called intestinal angina) after eating, especially fatty foods.
Symptoms of intestinal angina include a dull, cramping pain in the upper abdomen, although it can radiate to the back. Intestinal angina usually lasts two to three hours, but then returns after another meal .
Acute intestinal ischemia can occur when an embolism (blood clot) lodges in the arteries of the intestine. These blood clots most often form in the heart as a result of atrial fibrillation. If the stroke is severe enough, an intestinal infarction (death of part of the intestine) can occur. Intestinal infarction is a medical emergency .
Limb ischemia can occur with peripheral arterial disease (PAD) , a form of atherosclerosis that affects the arteries that supply the arms or legs (most commonly the legs) .
The most common syndrome seen in limb ischemia is intermittent claudication, a type of spasmodic pain that usually affects one leg and occurs reproducibly after some walking. PAD is often treated with angioplasty and stenting , although bypass surgery is often necessary as well.