myocardial infarction; MI; heart attack
A disorder in which damage to an area of heart muscle occurs because of an inadequate supply of oxygen to that area.
Common causes, incidence, and risk factors
Causes include clot formation or spasm in one of the arteries that supply the heart muscle (a coronary artery). These and other similar conditions block the supply of oxygen to an area of the heart, leading to damage or death of the cells in that area. Most often, this occurs in a coronary artery that has been narrowed from changes related to atherosclerosis. The damaged tissue results in a permanent loss of contraction of this portion of the heart muscle.
Risk factors for MI include smoking, hypertension, diabetes mellitus, high fat diet, high blood cholesterol (LDL) levels, obesity, male gender, age over 65, and heredity. A personal or family history of coronary artery disease, cerebrovascular disease, peripheral vascular disease, angina (particularly unstable angina), or kidney failure requiring hemodialysis indicates increased risk for MI. Occasionally, sudden overwhelming stress can trigger an MI, but this is rare. In older persons, straining to have a bowel movement can be a risk factor.
Chest pain is the cardinal symptom of MI, 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.
Acute MI occurs in approximately 2 out of 1,000 people per year. It is a major cause of sudden death in adults.
Control cardiac risk factors whenever possible. Control blood pressure and total cholesterol levels, reduce or avoid smoking, modify diet (increase high density lipoproteins & decrease low density lipoproteins) if necessary, control diabetes, lose weight if obese. Follow an exercise program to improve cardiovascular fitness. (Consult the health care provider first.)
After an MI, followup care is important to reduce the risk of developing a new MI. Often, a cardiac rehabilitation program is recommended to aid in gradual return to a "normal" lifestyle. Follow the exercise, diet, and/or medication regimen prescribed by your doctor.
- chest pain below the sternum (breastbone)
- back pain
- abdominal pain
- pain may radiate
to the chest, arms, shoulder
to the neck, teeth and jaw
to the back
- pain is prolonged, typically greater than 20 minutes
- pain similar to angina but not relieved by rest or nitroglycerin
- any prolonged chest pain, back pain, or abdominal pain
- pain that may be described as:
intense, severe, subtle, or absent
squeezing or heavy pressure
a tight band on the chest
"an elephant sitting on my chest"
- shortness of breath
may or may not be accompanied by pain
- lightheadedness - dizzy
- sweating, may be profuse (diaphoresis)
- dry mouth
- feeling of "impending doom"
Additional symptoms that may be associated with this disease:
- breathing, absent temporarily
- breathing difficulty, lying down
- blood pressure, low
- behavior, unusual or strange
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.
- An ECG, single or repeated over 2 to 3 days, often shows MI.
Indications of MI and extent of heart damage may show on the following tests:
- coronary angiography
- nuclear ventriculography (MUGA or RNV).
Byproducts of heart damage and factors indicating high risk for MI may show on the following tests:
- LDH isoenzymes
- CPK isoenzymes
This disease may also alter the results of the following tests:
- apolipoprotein B100
- apolipoprotein CII
- cholesterol test
- heart MRI
- lipids - serum
- myoglobin - serum
- myoglobin - urine