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heart attack Images (Click to view larger image)
Alternative Names
myocardial infarction, acute myocardial infarction, acute coronary syndrome, MI, AMI
Definition
A heart attack occurs when the heart muscle is deprived of oxygen. This causes cells of the heart tissue to die.
What is going on in the body?
Coronary arteries supply blood and oxygen to the heart. When these arteries do not deliver enough oxygen to the heart muscle, pain results. This pain is known as angina. It is a sign that the heart is not getting adequate blood and oxygen. If the heart muscle is deprived of oxygen for a long enough period of time, the heart cells begin to die. This results in a heart attack.
What are the signs and symptoms of the condition?
The most common symptom of a heart attack is chest pain or angina. Angina is often described as a feeling of crushing, pressure, fullness, heaviness, or aching in the centre of the chest. These sensations may extend into the neck, the jaw, and down the left arm. Angina is often associated with other symptoms, including: The type of angina known as stable angina is brought on by exertion, and relieved by rest or nitroglycerin. The type of angina known as unstable angina is more frequent and more severe. It can occur even when the person is resting. Unstable angina is a medical emergency.
Usually, angina is very uncomfortable. However, in some cases symptoms are mild enough to be discounted as merely flatulence or indigestion. Also, a person may deny that he or she is experiencing chest pain and delay seeking help. Someone who has diabetes may not experience classic angina symptoms. In many cases, the angina is so mild that the person with diabetes can have a heart attack without knowing it.
What are the causes and risks of the condition?
The buildup of fatty deposits along the inner wall of the artery, called arteriosclerosis, is the most common cause of heart attacks. The narrowing of coronary arteries, known as coronary artery disease, reduces the amount of oxygen-rich blood that can reach the heart. Some risk factors for developing a heart attack are: What can be done to prevent the condition?
Keeping high blood pressure, diabetes, and high cholesterol levels under control is important in reducing heart attack risk. Maintaining a healthy body weight, including physical activity in everyday life, and eating a diet designed to minimise heart disease can help prevent heart attacks.
How is the condition diagnosed?
A heart attack is most often diagnosed by abnormalities seen on an electrocardiogram, or ECG. Another diagnostic method is to measure the levels of certain enzymes that are released into the bloodstream during a heart attack. 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. A person can experience severe chest pain or angina without having a heart attack.
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.
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 treatment for a heart attack depends on the cause. The sooner the treatment begins, the better the chance the person will survive. The most important initial treatment is to stop the pain. 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 blood thinners are used once the person arrives in an emergency department. Some blood thinners are very powerful. These medications can actually dissolve the clot that is blocking the artery and causing the heart attack. Oxygen will be given to the individual through a face mask or a tube with prongs inserted into the nostrils. This increases the oxygen available to the heart muscle and helps minimise damage to the heart tissue. A medication known as nitroglycerin is administered to reduce the work of the heart. Morphine may be given as well to decrease pain, calm the person, and reduce the work the heart has to do.
A person who has had a heart attack often undergoes a procedure known as a cardiac catheterisation or cardiac angiogram. A contrast agent is injected into the coronary arteries. Using an X-ray procedure, the doctor 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 catheterisation may show blockage in many arteries. If this is the case, Heart bypass surgery, also known as coronary artery bypass graft or CABG, may be necessary. Heart bypass surgery is a procedure in which 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.
What are the side effects of the treatments?
Side effects of medications can include headache, dizziness, allergic reactions, and upset stomach. Blood thinning medications may increase the risk of bleeding and haemorrhage.
heart bypass surgery can cause bleeding, infection, allergic reaction to anaesthesia, and death.
Since the complications from a heart attack itself are significant, the risk of any treatment is usually less than the risk of allowing the heart attack to proceed without treatment.
What happens after treatment for the condition?
After the initial emergency treatment of a heart attack, the doctor will work to diagnose the underlying cause of the heart attack. For example, treatment will focus on control of blood pressure if high blood pressure is identified as the cause. Likewise, the doctor will work with the individual to control high cholesterol levels, diabetes, smoking, obesity, and other identified causes.
How is the condition monitored?
Following recovery from the heart attack, a person will need to visit the doctor regularly so medications can be adjusted. The doctor will monitor blood pressure, weight, and other significant factors such as blood sugar in a person with diabetes. Regular exercise treadmill ECG tests may be done to make sure that there is proper blood flow to the heart. Any new or worsening symptoms should be reported to the doctor.
Author: Vincent J. Toups, MD
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Contributors
Potential conflict of interest information for reviewers available on request |
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