Heart Attack - Causes

Heart attacks are usually caused by severe coronary artery disease (CAD). CAD is any condition that affects the coronary arteries. The coronary arteries are the blood vessels that supply blood to the heart. Plaque in an artery is a common type of coronary artery disease.

Major Risk Factors

A number of risk factors increase the chance of developing coronary artery disease. Some major risk factors can be changed and others cannot. Among those that cannot be changed are the following:

• Heredity. People whose parents have CAD are more likely to develop the condition. African Americans are also at increased risk for CAD.
• Gender. Men under the age of sixty are more likely to have heart attacks than women of the same age.
• Age. Men over the age of forty-five and women over the age of fifty-five are at higher risk than younger people. People over the age of sixty-five are more likely to die of a heart attack.

Some risk factors that can be changed are:

• Smoking. Smokers are more than twice as likely to have a heart attack than nonsmokers. They are 2 to 4 times more likely to die of a heart attack.
• High cholesterol. Cholesterol is a material that occurs naturally in all animals, including humans. It has many important biological functions. High levels of cholesterol in the blood, however, may increase the chance that plaque will form in blood vessels. It contributes to the risk of CAD and heart attack.
• High blood pressure. High blood pressure (see hypertension entry) makes the heart work harder. Over time, the heart becomes weaker. High blood pressure also increases the risk of stroke, kidney failure, and other types of heart disease.
• Lack of physical exercise. Even modest physical activity can be helpful if done regularly.

Contributing Risk Factors

Other conditions may affect the risk of CAD and heart attack. Scientists are not certain how these factors are involved in these conditions, however. The factors are:

• Diabetes mellitus (see diabetes mellitus entry). People with diabetes are at much higher risk for heart attack. About 80 percent of all diabetics die of some type of heart or blood vessel disease.
• Obesity (see obesity entry). Excess weight places a strain on the heart. It increases the risk of CAD and heart attack.
• Stress and anger. Stress and anger both increase blood pressure and heart rate. Some researchers think that these emotions can contribute to the chance of heart attack.

Most heart attacks are caused by blood clots that form on atherosclerotic plaque, which block a coronary artery from supplying oxygen-rich blood to part of the heart, as highlighted in the illustration above. (Illustration by

Andrew Bezear, Reed business Publishing

. Reproduced by permission of

Science Photo Library and Photo Researchers, Inc.

)

Many of the above risk factors are related to each other. For example, obesity and stress both contribute to high blood pressure. People with more than one risk factor are even more likely to develop CAD and have a heart attack.