Alternate Names: Myocardial infarction; MI; Acute MI
Causes and Risks:
Heart attacks are often caused by a clot that blocks one of the coronary arteries (the blood vesselsthat bring blood and oxygen to heart muscle). The clotpreventsblood and oxygen from reaching that area of the heart, leading to the death of heart cells in that area. Usually, this occurs in a coronary artery that has been narrowed from changes related to atherosclerosis. The damaged heart tissue permanently loses its ability to contract.
The risk factors forheart attackinclude:
A personal or family history of coronary artery disease, cerebrovascular disease, peripheral vascular disease, angina (particularly unstable angina), or kidney failure requiring hemodialysis alsoincrease therisk for heart attack.
Occasionally, sudden overwhelming stress can trigger a heart attack, but this is rare. In older persons, straining to have a bowel movement can be a risk factor.
Newer risk factors for coronary artery disease havebeen identifiedover the past several years, including elevated homocysteine levels, elevated c-reactive protein, and apo-a.Homocysteine levels can be treated with folic acid supplements in the diet. Studies are still ongoing about the practical value of these new markers.
Chest pain is a major symptom of heart attack, but in many cases the pain may be subtle or even completely absent, especially in the elderly and diabetics. Other symptoms such as weakness, shortness of breath, nausea, or vomiting may predominate.
Heart attack accounts for1 out of every5 deaths. It is a major cause of sudden death in adults.
Prevention:
Control cardiac risk factors whenever possible. Control blood pressure and total cholesterol levels, reduce or avoid smoking, modify diet if necessary (increase high density lipoproteinsand decrease low density lipoproteins), control diabetes, and lose weight if obese. Follow an exercise program to improve cardiovascular fitness. (Consultyour health care provider first.)
After a heart attack, follow-up care is important to reduce the risk of developing a new heart attack. Often, a cardiac rehabilitation program is recommended to help you gradually return to a "normal" lifestyle. Follow the exercise, diet, and/or medication regimen prescribed by your doctor.
Symptoms:
Additional symptoms that may be associated with heart attack:
Note: The victim commonly denies that he or she may be having a heart attack. The person may have no symptoms (i.e., they are having a "silent attack.")
Signs and Tests:
Examination often reveals a rapid pulse. Blood pressure may be normal, high, or low. Listening to the chest with a stethoscope (auscultation) may show crackles in the lungs, heart murmur, or other abnormal sounds.
Heart attack and the extent of heart damage may also show on the following tests:
The byproducts of heart damage and factors indicating high risk forheart attackmay show on the following tests:
This disease may also alter the results of the following tests:
Treatment:
A heart attack is a medical emergency! Hospitalization is usually required for 1 to 14 days. Treatment may include intensive care and involve emergency surgery. ECG monitoring isstarted immediately, because life-threatening dysrhythmias are the leading cause of death in the first few hours after a heart attack.
The goal of treatment is to reduce the demands on the heart so that it can heal, and prevent and treat complications. Activity may be restricted initially, then gradually increased.
An intravenous catheter will be inserted to administer emergency medications and fluids. Various monitoring devices may be neccessary. A urinary catheter may be inserted to closely monitor fluid status.
Oxygen is usually given, even if blood oxygen levels are normal. This makes oxygen readily available to the tissues of the body and reduces the workload of the heart.
Diet may or may not be restricted. Diet restrictions often include low salt intake, no caffeine, and low fat.
MEDICATIONS
Morphine is the analgesic most often given for pain. Nitrates such as nitroglycerin are given for pain and to reduce the oxygen requirements of the heart. Beta-blockers (metoprolol and atenolol) reduce the workload of the heart. Digitalis improves the heart’s pumping action. Calcium channel blockers reduce oxygen requirements in the heart muscle. Anti-arrhythmics and diuretics may also be prescribed.
Clot-dissolving (thrombolytic) therapy is usually initiated within 6 hours of when chest pain begins. The initial therapy will include an IV infusion of clot-dissolving medication (streptokinase or tissue plasminogen activator) immediately followed by IV infusion of heparin. Heparin therapy will last for 48 to 72 hours. Additionally, oral aspirin and warfarin may be prescribed to prevent further development of clots.
Thrombolytic therapy is not appropriate for people who have had:
- Amajor surgery, organ biopsy, or major trauma within the past 6 weeks
- Recent neurosurgery
- Head trauma within the past month
- History of GI (gastrointestinal) bleed
- Intracranial tumor
- Stroke within the past 6 months
- The person is currently pregnant
Possible complications of thrombolytic therapy include bleeding and hemorrhage.
SURGERY
Emergency angioplasty may be required to open blocked coronary arteries. Emergency coronary artery bypass surgery (CABG) may be required in some cases.
Support Groups: The stress of illness can often be helped by joining a support groupwhere members share common experiences and problems. See heart disease - support group.
Prognosis:
The expected outcome varies with the amount and location of damaged tissue. The outcome is worse if there is damage to the electrical conduction system (the impulses that guide heart contraction).
Approximately 1/3 of cases are fatal. If theperson is alive 2 hours after an attack, the probable outcome for survival is good, but may include complications. Uncomplicated cases may recover fully. Heart attacks are not necessarily disabling.Usually,the person can gradually resume normal activity and lifestyle, including sexual activity.
Complications:
Go to the emergency room or call the local emergency number (such as 911) if crushing chest pain or other symptoms suggestive of heart attack occur.
