Health Guide » 
Overview
What is a heart attack?
A heart attack occurs when one or more of the coronary arteries is blocked, depriving heart muscle of oxygen-rich blood. Without blood supply, the heart muscle cells die. If a large area of the heart is damaged by a heart attack, it can cause sudden death.
A blockage usually occurs when a plaque inside the coronary artery breaks open and a blood clot forms around it. See an illustration of how plaque causes a heart attack.
Heart attack (the medical term is myocardial infarction, or MI) is a serious condition that requires immediate treatment to restore blood flow.
What's the difference between stable and unstable angina, and why is unstable angina a concern?
Angina is a type of chest pain that occurs when there is not enough blood flow to the heart muscle, often the result of narrowing of blood vessels that supply blood to the heart muscle. Angina is termed either stable or unstable.
Stable angina occurs at predictable times with a specific amount of exertion or activity. It is relieved by rest and may continue without much change for years. Stable angina usually is relieved by rest or nitrates (nitroglycerin) and usually lasts less than 20 to 30 minutes.
Unstable angina is a change in the usual pattern of stable angina caused by reduced blood flow to the heart. In unstable angina, chest pain occurs at rest or with less and less exertion, may be more severe and last longer, or no longer responds to nitroglycerin. Unstable angina means that impaired blood flow has gotten worse because of increased narrowing in the coronary artery. Unstable angina is a warning sign that a heart attack may soon occur unless treated.
Because unstable angina can progress to a heart attack, it requires immediate medical attention.
What are the symptoms of a heart attack?
The most common symptom of a heart attack is severe angina, or chest pain, also described as discomfort, pressure, squeezing, or heaviness. Many people also have at least one of the following:
Pain or discomfort that radiates to the back, jaw, throat, or arm
Discomfort in the upper abdomen, often mistaken for "heartburn"
Sweating, nausea, and vomiting
Difficult breathing, palpitations, dizziness, and fainting
Weakness, numbness, and anxiety
However, chest pain is not always present. In a recent review of 700 people treated for heart attack, 47% came to the emergency room because they had symptoms other than chest pain, including shortness of breath, dizziness, weakness or fainting, and abdominal pain.1 Women, older adults, and people with Diabetes are more likely to have atypical symptoms and less likely to have chest pain during a heart attack.
It is possible to have a "silent heart attack" without any symptoms, although this is rare.
Unstable angina is a change in the usual pattern of angina. It is characterized by chest pain that is new and limits your normal activities, suddenly becomes more frequent and severe, or occurs at rest or with minimal exertion.
What causes a heart attack?
The underlying cause of unstable angina and heart attack is diminished blood flow to the heart. In most cases, this results from plaque buildup and rupture in the coronary arteries. Some plaques, called unstable plaques, are prone to rupture or tear. When this happens, a clot forms over the ruptured area and may block blood flow in the artery. When the heart muscle does not receive enough oxygen-rich blood, the muscle is damaged, and a heart attack occurs. See an illustration of how an unstable plaque causes a heart attack. If the blood flow is partially blocked or blocked for a short period of time and then resolves, it is called unstable angina.
Plaque buildup on the inside of your arteries anywhere in your body is called atherosclerosis. When plaque buildup occurs in the heart arteries, it is called coronary artery disease. Plaque is made up of excess cholesterol, calcium, and other substances that float in your blood and, over time, accumulate on the inside walls of your coronary arteries. Atherosclerosis is usually the result of years of high levels of "bad" (LDL) cholesterol, high blood pressure, smoking, and other risk factors. See an illustration of an artery blocked by atherosclerosis.
Sudden intense exercise, sudden strong emotion, or drug use, for example, can trigger a heart attack by causing a rapid rise in blood pressure, a surge in catecholamines, and other physical reactions. However, in most cases, there is no clear reason why heart attacks occur.
Plaque is not always the culprit in heart attack. In rare cases, the coronary artery spasms, obstructs blood flow, and causes chest pain. If severe, spasm can block blood flow and cause a heart attack. Most of the time in these cases, atherosclerosis is also involved, although sometimes the arteries are clear. Cocaine can cause coronary artery spasm and heart attack, although in most cases it is not known what triggers them.
What should I do if I think I am having a heart attack?
If you think you may be having a heart attack or unstable angina, it is critical to get treatment as soon as possible. First, call 911 or other emergency services, describe your symptoms, and relay that you could be having a heart attack. Paramedics will respond to your call in a few minutes and are equipped to handle life-threatening abnormal heart rhythms that often occur with heart attack. If you cannot reach emergency services, have someone drive you to the hospital right away. Do not drive yourself unless you have absolutely no other option.
If you think you may be having a heart attack but are not sure, call 911 and describe your symptoms. A "wait-and-see" approach can be fatal in these circumstances.
After calling for help, chew a regular-strength aspirin. A recent study showed that those who took aspirin during their heart attack and for 1 month after were less likely to die from a subsequent heart attack or stroke than those who did not take aspirin.2
Unstable angina can lead to a heart attack or even cardiac arrest (when the heart stops). If you think you are experiencing unstable angina, take the above precautions as though you were having a heart attack.
When you arrive at the emergency room you will be quickly evaluated and usually have an electrocardiogram (EKG, ECG). Several blood tests will be done, including tests to see whether cardiac enzymes are elevated, an indication of heart muscle damage. If your doctor suspects heart problems, you will be closely monitored and receive oxygen and medications that control pain and decrease the workload on the heart.
How is a heart attack treated?
Quick treatment for a heart attack or unstable angina is critical. If blood supply can be rapidly restored to the heart, damage to heart tissue may be prevented (in unstable angina) or more heart tissue can be saved from permanent damage. On the way to the hospital or in the emergency room, you probably will be given an aspirin. In addition to aspirin, other medications that prevent blood clots from forming or that break up blood clots may be given through a needle in your vein. These medications must be given within a few hours of the start of your heart attack to be effective. Other medications to help decrease your heart's workload, ease your pain, and prevent any life-threatening abnormal heart rhythms are often also given.
If your doctor thinks you may need angioplasty, you may be taken directly to the cardiac catheterization lab for evaluation of your coronary arteries. A cardiac catheterization can indicate whether you need further therapy. During the catheterization procedure, your doctor may decide to reopen a blocked artery by performing angioplasty and inserting a stent, which is a small, coiled wire-mesh tube, inside the artery's blocked area. If necessary, emergency coronary artery bypass surgery may be done.
You will probably be started on medications, such as ACE inhibitors, beta-blockers, and cholesterol-lowering medications (called statins), to prevent another heart attack or heart failure. Usually, you continue to take these and possibly other medications after you leave the hospital.
If you have unstable angina, you will be treated with medications to reduce your heart's workload and to prevent a blood clot from growing larger. Depending upon your symptoms and the results of your tests, your doctor may recommend medications and/or angioplasty.
Am I at risk for having a heart attack?
You may be at increased risk if you answer "yes" to any of these questions:
Do you smoke? | Yes | No |
Are you a woman over 55 years old, or are you a man over 45 years of age? | Yes | No |
Did your father or brother have a heart attack before age 55 or your mother or sister have one before age 65? | Yes | No |
Do you have Diabetes or a fasting blood sugar of 126 mg/dL or higher or do you need medicine to control your blood sugar? | Yes | No |
Is your blood pressure 140/90 mm Hg or higher, or have you been told by your doctor that your blood pressure is too high? | Yes | No |
Do you get less than a total of 30 minutes of physical activity on most days? | Yes | No |
Has a doctor told you that you have angina (chest pains) or have you had a heart attack? | Yes | No |
Has your doctor told you that your total cholesterol level is 200 mg/dL or higher or your HDL (good cholesterol) is less than 40 mg/dL? | Yes | No |
Do you have a body mass index (BMI) score of 25 or more? | Yes | No |
If you do not know your BMI, blood pressure or cholesterol, check with your health care provider.
