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Overview of Myocardial Infarction (Heart Attack)
Myocardial infarction (heart attack) is a serious result of coronary
artery disease. Coronary artery disease occurs from atherosclerosis, when arteries
become narrow or hardened due to cholesterol plaque build-up. Further narrowing may occur
from thrombi (blood clots) that form on the surfaces of plaques. Myocardial infarction
occurs when a coronary artery is so severely blocked that there is a significant reduction
or break in the blood supply, causing damage or death to a portion of the myocardium
(heart muscle). Depending on the extent of the heart muscle damage, the patient may
experience significant disability or die as a result of myocardial infarction.
In addition to atherosclerosis, myocardial infarction may result from a temporary
contraction or spasm of a coronary artery. When this occurs, the artery narrows and the
blood flow from the artery is significantly reduced or stopped. Though the cause of
coronary artery spasm is still unknown, the condition can occur in both normal blood
vessels and those partially blocked by plaques.
Risk factors for Myocardial Infarction (Heart Attack)
The following risk factors have been associated with a higher incidence of myocardial
infarction. Some of these risk factors are controllable (such as smoking and physical
activity) while others are uncontrollable (such as age, genetics, family history).
- Age: Four out of five patients with coronary artery
disease are 65 years of age or older. After menopause, females are more likely to die
within the first year of having a myocardial infarction than males.
- Gender: Males are at higher risk of myocardial infarction than women, and males are
also more likely to suffer myocardial infarction earlier in life. However, heart disease
kills more females each year than any other disease, including breast cancer. An alarming survey reported
by the American Heart Association found that only 8% of women perceive heart disease as
the greatest threat to their health despite the fact that heart disease is the leading
cause of death among both women and men. Over 500,000 American women die from
cardiovascular disease each year--twice the number of deaths from all cancers
combined. Also, women are more likely to die within the first year of a heart attack than men.
- Family history/race: A family history of heart disease increases the risk of
coronary artery disease and myocardial infarction. In the United States, African Americans
tend to have more severe high blood pressure than Caucasians, increasing coronary artery
disease/myocardial infarction risk. The incidence of heart disease is also higher among
certain population groups such as Mexican Americans, American Indians, native Hawaiians
and some Asian Americans.
- Smoking: Cigarette smokers are twice as likely to experience myocardial infarction
compared to non-smokers. Smokers also have a two to four time higher risk of sudden
cardiac death (within an hour of a heart attack).
- High blood pressure (hypertension): Alone or in association with obesity, smoking,
high blood cholesterol levels or diabetes, high blood pressure increases the risk of
myocardial infarction and stroke.
- High blood cholesterol: High total and low-density lipoprotein (LDL
cholesterol) levels and low HDL cholesterol levels increase the risk of myocardial
infarction Cholesterol levels can be lowered with dietary/lifestyle modifications such as
exercise or medications.
- Obesity: Obesity increases coronary artery
disease, myocardial infarction, and stroke risk. Obesity increases strain on the heart,
raises blood pressure and cholesterol, and increases diabetes risk. Weight reduction can
be achieved with modifications to diet and increased physical activity.
- Diabetes: Approximately two-thirds of patients with diabetes die from heart or blood
vessel disease. Adults with diabetes are three to seven times more likely to develop heart
disease. A recent recommendation from the U.S. government advocates aggressive treatment
of high cholesterol in people with diabetes.
- Lack of physical activity: Regular exercise reduces the risk of coronary artery
disease and myocardial infarction by controlling blood cholesterol levels, decreasing the
risk of obesity or diabetes, and lowering blood pressure levels in some patients.
- Stress: Research indicates a possible relationship between stress and
coronary artery disease, which may lead to myocardial infarction Hypertension (high blood
pressure) and high cholesterol are associated with stress, as are increased tendencies to
smoke, gain weight and/or decrease physical activity.
Warning Signs of Myocardial Infarction (Heart Attack)
When a heart attack occurs, time is essential. Patients have much better chances of
survival if they proceed immediately to an emergency room when symptoms occur. The most
common symptom of myocardial infarction is angina (chest pain). Myocardial infarction
frequently occur from 4:00 a.m. to 10:00 a.m. since increased amounts of adrenaline are
usually released in the morning. Adrenaline normally helps regulate blood pressure, heart
rate, and blood glucose concentration.
| Common
Heart Attack Warning Signs
Uncomfortable pressure, fullness, squeezing or pain in the center of the chest lasting
more than a few minutes
Pain spreading to the shoulders, neck or arms.
Chest discomfort with lightheadedness, fainting, sweating, nausea or dyspnea (shortness
of breath).
|
Other signs of myocardial infraction may include:
- Sweating
- Jaw pain
- Heartburn or indigestion
- Upper back pain
- General feeling of illness
A recent survey reported by the American Heart Association reveals that the majority of American women do not
understand the true threat of cardiovascular disease. Despite the fact that heart disease is the leading cause
of death among women, a nationwide survey revealed that only 8% of women perceive heart disease as the greatest
threat to their health. More than six out of 10 women falsely believe that they are more likely to develop cancer
than heart disease.
Other statistics from the American Heart Association:
- Over 500,000 American women die of cardiovascular disease each year. This twice the number of deaths from all
cancers combined (lung cancer, the leading cause of cancer deaths, claims approximately 65,000 deaths per year,
and breast cancer kills around 40,000 women per year).
- One in five women have some form of heart or blood vessel disease.
- 38% of women who have heart attacks die within the first year compared to 25% of men.
- 35% of women have a second heart attack within six years of the first attack compared to 18% of men.
- Over 60,000 women die of stroke each year; approximately 60% of stroke deaths occur in women.
Diagnosing Myocardial Infarction (Heart Attack)
When symptoms are presented, patients should be evaluated quickly with blood tests and
an electrocardiogram. After the patient is stabilized, an echocardiogram and nuclear
medicine exam may be performed.
- Blood work: Blood tests will be performed to detect levels of creatine
phosphokinase (CPK), aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and
other enzymes released during myocardial infarction.
- Electrocardiogram (ECG or EKG): An electrocardiogram makes a graphic record
of the cardiac activity, either on paper or a computer monitor. An ECG can be beneficial
in detecting disease and/or damage.
- Echocardiogram (heart ultrasound): This diagnostic technique is an excellent
first step in investigating congenital heart disease or in evaluating abnormalities of the
heart wall. Echocardiography is a non-invasive exam in which images are acquired and
viewed in real time without the use of radiation. Echocardiography is often useful in
studying the beating heart and provides some information on functional abnormalities of
the heart wall, valves and blood vessels. Doppler ultrasound can be used to measure blood
flow across a heart valve. Abnormal operation of the valves can be detected by studying
the opening and closing function versus normal valve function. Echocardiography may also
be used to study congenital heart defects such as a septal defect (a hole in the wall that
separates the two chambers of the heart).
- Nuclear medicine: Nuclear medicine (also
called radionuclide scanning) allows visualization of the anatomy and function of an
organ. The patient will be given a radionuclide which will assist in the acquisition clear
images of the heart with a gamma camera. Nuclear medicine imaging may be used to detect
coronary artery disease, myocardial infarction, valve disease, heart transplant rejection,
check the effectiveness of bypass surgery, or to select patients for angioplasty or
coronary bypass graft.
Treating Myocardial Infarction (Heart Attack)
Treatment options for myocardial infarction include medications such as antiplatelets
(aspirin), beta blockers, calcium channel blockers, ACE inhibitors, etc. Additional
treatment with coronary angioplasty (may be followed with stenting—see below) may be
necessary. Depending on the patient’s condition and reasons for suffering myocardial
infarction, coronary artery bypass graft may or may not be performed.
The following chart summarizes types of drugs that may be used to help treat myocardial
infarction. Brand names of drugs are shown in parentheses.
| Type
of Drug |
Function |
Examples |
| Beta blockers |
reduce heart’s
workload |
nadolol (Corgard),
metoprolol (Lopressor, Toprol XL), pindolol (Visken), bisoprolol (Zebeta), acebutolol
(Sectral). |
| Diuretics |
rid body of excess
fluid and salt |
hydrochlorothiazide
(HydroDIURIL), chlorothiazide (Diuril), furosemide (Lasix), bumetanide (Bumex),
spironolactone (Aldactone), triamterene (Dyrenium), metolazone (Zaroxolyn). |
| ACE inhibitors |
prevent blood vessel
constriction |
benazepril
(Lotensin), lisinopril (Prinivil), captopril (Capoten), ramipril (Altace), fosinopril
(Monopril), moexipril (Univasc). |
| Calcium channel
blockers |
increase blood flow
through the heart and help prevent blood vessel constriction by blocking calcium ions |
verapamil (Calan,
Isoptin, Verelan), diltiazem (Cardizem, Tiamate, etc.), nifedipine (Adalat) |
| Nitrates |
help relax the
myocardium and blood vessels, enabling oxygen-rich blood to reach the heart. |
nitroglycerin
(Deponit, Nitrek, Nitrol, etc.), isosorbide dinitrate (Dilatrate-SR) |
| Antiplatelets |
help prevent thrombi
(blood clots) |
aspirin |
A note about heart attack prevention: While several studies have found that a low-dose aspirin regimen
may reduce the risk of first heart attacks in men, a 2005 study conducted by
researchers at the U.S. National Heart, Lung, and Blood Institute found that the effects of aspirin may
not be the same in women. In the study of 45,000 women followed over a ten-year period, aspirin generally
did not prevent first heart attacks or deaths from cardiovascular disease in women. However, the researchers
did find some benefits of aspirin in women over 65 years of age. Most notably, these women had a significantly
lower risk of stroke. An aspirin regimen typically consists of a 100 milligram aspirin on alternate days. The
study suggests this regimen may be beneficial for women 65 years of age and older but for young women, the
possible benefits of aspirin should be weighed against possible side effects including internal bleeding.
Medical procedures used to help treat myocardial infarction include:
- Coronary angioplasty: Involves placing a catheter with a small balloon on its tip
into the patient’s narrowed artery. When properly positioned, the balloon is inflated
and deflated, moving the plaque build-up further against the artery wall and thereby
improving the flow of blood. This procedure may also be called percutaneous transluminal
coronary angioplasty (PCTA), coronary artery balloon dilation or balloon angioplasty.
Coronary angioplasty may be followed by stenting, a procedure in which a stent (expandable
wire mesh tube) is permanently inserted into the artery to keep it open and restore normal
blood flow.
- Coronary artery bypass graft: Involves grafting the ends of a healthy blood vessel
(often taken from the chest or leg) above and below a narrowed artery, bypassing the flow
of blood around the narrowed artery. Bypass surgery can relieve symptoms of coronary
artery disease, such as angina (chest pain) and dyspnea (shortness of breath) and may be
used to prevent or treat myocardial infarction.
Updated: August 2006
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