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Heart Attack

Heart Attack

Alternate Names

  • myocardial infarction
  • MI
  • Heart attack


A heart attack, also called a myocardial infarction (MI), occurs when the heart muscle is deprived of oxygen to the point that the heart tissue dies.

What is going on in the body?

The left and right coronary arteries are the first branches to leave the aorta, the main artery of the body. The coronary arteries supply blood and oxygen to the heart muscle. When these arteries do not deliver enough oxygen, a pain known as angina results. If the heart muscle is deprived of oxygen for a long enough period of time, the heart cells begin to die. This is called a heart attack.


What are the causes and risks of the condition?

Atherosclerosis is the most common cause of heart attacks. Deposits of fat, platelets, and cellular debris build up along the inner wall of the artery. The narrowing of the coronary arteries from atherosclerosis is known as coronary heart disease. It reduces the amount of oxygen-rich blood that can reach the heart.
Some risk factors for developing a heart attack are:
  • diabetes
  • family history of coronary artery disease
  • high blood pressure, also called hypertension
  • high cholesterol
  • lack of exercise
  • obesity
  • smoking


What can be done to prevent the condition?

Heart attacks cannot always be prevented. It is important to control high blood pressure, diabetes, and high cholesterol. A person can lower his or her risk by maintaining a healthy body weight. Physical activity and a diet designed to reduce heart disease can help prevent heart attacks.
The American Heart Association does not recommend hormone therapy (HT) in menopausal women or vitamin therapy to prevent heart disease.
For some people, taking a daily dose of aspirin may reduce the risk of first or subsequent heart attacks. However, risks of taking aspirin include bleeding. Therefore, it is recommended that all adults discuss with their personal physician the risk and benefits of daily aspirin therapy.
Maintaining normal lipid levels (total cholesterol, HDL cholesterol, LDL cholesterol and triglycerides) can prevent heart attacks. Also, maintaining a normal blood sugar reduces the risks of heart attack.


How is the condition diagnosed?

Diagnosis of a heart attack begins with a history and physical exam. An electrocardiogram (ECG) can help in the diagnosis. Blood tests are done to measure levels of certain enzymes (released by damaged heart muscle) in the bloodstream. Because these enzymes may not rise for several hours after the pain begins, a person with a suspected heart attack is often admitted to a hospital. Rechecks of these levels over a period of time will determine if a heart attack has occurred.

Long Term Effects

What are the long-term effects of the condition?

Depression can occur following a heart attack. Most people who survive for a few days after a heart attack can expect a full recovery. However, about 10% of people who have a heart attack die within a year.

Other Risks

What are the risks to others?

Heart attacks are not contagious and pose no risk to others.


What are the treatments for the condition?

The sooner treatment begins, the better the chance the person will survive. Taking an aspirin as early as possible after the onset of pain is very important. Aspirin acts as a blood thinner. This helps get oxygen-rich blood to the oxygen-deprived heart muscle.
Other medications are used once the person arrives in an emergency department. Powerful medications called thrombolytics ("clot-busters") can sometimes dissolve the clot that is blocking the artery and causing the heart attack. Oxygen will be given to reduce damage to the heart tissue.
A medicine known as nitroglycerin (i.e., Nitrolingual, Nitroquick, NitroStat) is given to decrease the work of the heart. Morphine may be given as well to reduce pain and decrease the work the heart has to do.
A person who has had a heart attack often undergoes a procedure known as a cardiac catheterization or cardiac angiogram. A contrast agent is injected into the coronary arteries. Using an X-ray procedure, the healthcare professional can watch the blood flow through the heart and see if a blockage has occurred.
Some blockages in the coronary arteries can be opened using a special catheter with a balloon on the end. This balloon is inserted through the narrowed artery and inflated to open the artery and allow blood to flow. This procedure is called balloon angioplasty. If the artery will not stay open, a stent, or hollow tube, can be inserted to hold the artery open.
The cardiac catheterization may show blockage in many arteries. If this is the case, heart bypass surgery may be necessary. A blood vessel from another part of the body is grafted onto the coronary artery. The graft provides a new route for blood to get to the heart muscle.
After recovery from the acute phase of the heart attack, the person may be enrolled in a cardiac rehabilitation program. This gradual exercise program will help the person safely resume a healthy lifestyle.

Side Effects

What are the side effects of the treatments?

Side effects of medicines can include headache, dizziness, allergic reactions, and upset stomach. Blood-thinning and clot-busting medicines may increase the risk of bleeding and hemorrhage. Heart bypass surgery can be complicated by bleeding, infection, reactions to anesthesia, and, rarely, death.

After Treatment

What happens after treatment for the condition?

After the initial emergency treatment of a heart attack, any underlying disorders will be treated. These include high blood pressure, high cholesterol, diabetes, smoking, and obesity.


How is the condition monitored?

The person will need to visit the healthcare professional regularly so medicines can be adjusted. He or she will monitor blood pressure, weight, and other major factors. Regular stress ECGs may be done to make sure there is proper blood flow to the heart. Any new or worsening symptoms should be reported to the healthcare professional.


Harrison's Principles' of Internal Medicine.

Rosen's Emergency Medicine: Concepts and clinical practice.

Merck Manual, 2000

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