Ischemia Health Article

Definition

Ischemia is an insufficient supply of oxygenated blood to an organ, usually due to a blocked artery.

Description

Myocardial ischemia is an intermediate condition in coronary artery disease during which the heart tissue is slowly or suddenly starved of oxygen and other nutrients. Eventually, the affected heart tissue will die. When blood flow is completely blocked to the heart, ischemia can lead to a heart attack. Ischemia can be silent or symptomatic. According to the American Heart Association, up to four million Americans may have silent ischemia and be at high risk of having a heart attack with no warning.

Symptomatic ischemia is characterized by chest pain called angina pectoris. The American Heart Association estimates that nearly seven million Americans have angina pectoris, usually called angina. Angina occurs more frequently in women than in men, and more often in African-Americans and Hispanics than in Caucasians. It also occurs more frequently as people age—25% of women over the age of 85 and 27% of men between 80 and 84 years of age have angina.

People with angina are at risk of having a heart attack. Stable angina occurs during exertion, can be quickly relieved by resting or taking nitroglycerine, and lasts from three to 20 minutes. Unstable angina, which increases the risk of a heart attack, occurs more frequently, lasts longer, is more severe, and may cause discomfort during rest or light exertion.

Ischemia also can occur in the arteries of the brain, where blockages can lead to a stroke. About 80–85% of all strokes are ischemic. Most blockages in the cerebral arteries are due to a blood clot, often in an artery narrowed by plaque. Sometimes, a blood clot in the heart or aorta travels to a cerebral artery. A transient ischemic attack (TIA) is a "mini-stroke" caused by a temporary deficiency of blood supply to the brain, or by a blood clot briefly blocking a cerebral artery. It occurs suddenly, lasts a few minutes to a few hours, and is a strong warning sign of an impending stroke. Ischemia can also affect intestines, legs, feet, and kidneys. Pain, malfunctions, and damage in those areas may result.

Causes & symptoms

Ischemia almost always is caused by blockage of an artery, usually due to atherosclerotic plaque. Myocardial

ischemia also is caused by blood clots (which tend to form on plaque), artery spasms or contractions, or any of these factors combined. Silent ischemia usually is caused by emotional or mental stress or by exertion, but there are no symptoms. Angina usually is caused by increased oxygen demand when the heart is working harder than usual, for example, during exercise, or during mental or physical stress. According to researchers at Harvard University, physical stress is harder on the heart than mental stress.

Risk factors

The risk factors for myocardial ischemia are the same as those for coronary artery disease, TIA, and stroke:

• Heredity. People whose parents have coronary artery disease are more likely to develop it. African-Americans also are at higher risk.
• Sex. Men are more likely to have heart attacks than women, and to have them at a younger age. Angina is more likely to occur in women.
• Age. Men who are 45 years of age and older and women who are 55 years of age and older are considered to be at risk. Risk also increases with age.
• Smoking. Smoking increases both the chance of developing coronary artery disease and the chance of dying from it. Secondhand smoke also may increase risk.
• High cholesterol levels. Risk of developing coronary artery disease increases as blood cholesterol levels increase. When combined with other factors, the risk is even greater.
• High blood pressure. High blood pressure makes the heart work harder, and with time, weakens it. When combined with obesity, smoking, high cholesterol levels, or diabetes, the risk of heart attack or stroke increases several times.
• High fibrinogen levels. Fibrinogens are the proteins involved in blood clotting and plaque formation.
• High homeocysteine levels. Homeocysteine also is involved in plaque formation.
• Oxidant damage, as indicated by high lipid peroxide levels. High lipid peroxide levels represent a high level of free radical damage and antioxidant deficiency.
• Lack of physical activity. Lack of exercise increases the risk of coronary artery disease.
• Diabetes mellitus. The risk of developing coronary artery disease is seriously increased for diabetics.
• Obesity. Excess weight increases the strain on the heart and increases the risk of developing coronary artery disease, even if no other risk factors are present. Obesity increases blood pressure and blood cholesterol, and can lead to diabetes.
• Stress and anger. Some scientists believe that stress and anger can contribute to the development of coronary artery disease. Stress increases the heart rate and blood pressure and can injure the lining of the arteries. Angina attacks often occur after outbursts of anger, as do many heart attacks and strokes.

Angina symptoms include:

• a tight, squeezing, heavy, burning, or choking pain that is usually beneath the breastbone—the pain may spread to the throat, jaw, or one arm
• a feeling of heaviness or tightness that is not painful
• a feeling similar to gas or indigestion
• attacks brought on by exertion and relieved by rest

If the pain or discomfort continues or intensifies, immediate medical help should be sought, ideally within 30 minutes.

TIA symptoms include:

• sudden weakness, tingling, or numbness, usually in one arm or leg or both the arm and leg on the same side of the body, as well as sometimes in the face
• sudden loss of coordination
• loss of vision or double vision
• difficulty speaking
• vertigo and loss of balance