Heart Attack
(Myocardial Infarction)
Medical Authors and Editors: Daniel
Kulick, MD, FACC, FSCAI
and Dennis Lee, MD
Medical Editors: Jay Marks, MD
and William C. Shiel, Jr., MD, FACP, FACR
Heart Attack Symptoms and Early Warning Signs
Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: Dennis Lee, MD
Heart
attack is the number one killer of both men and
women in the U.S. Each year, about 1.1 million Americans suffer a heart attack,
and 460,000 of these are fatal. Most of the deaths from heart attacks are caused
by ventricular fibrillation of the heart that occurs before the victim of the
heart attack can reach an emergency room. Those who reach the emergency room
have an excellent prognosis; survival from a heart attack with modern treatment should exceed 90%.
The 1% to 10% of heart attack victims who die later include those victims who
suffer major damage to the heart muscle initially
or who suffer additional damage at a later time. Fortunately, procedures such as
coronary angiogram and
PTCA (coronary balloon angioplasty), and clot dissolving drugs are available that can quickly open
blocked arteries in order to restore circulation to the heart and limit heart
muscle damage. In order to optimally benefit heart attack victims and limit the
extent of heart damage, these treatments to open blocked arteries should be
given early during a heart attack.
Knowing the early warning signs of heart attack is critical for prompt
recognition and treatment. Many heart attacks start slowly, unlike the dramatic
portrayal often seen in the movies. A person experiencing a heart attack may not
even be sure of what is happening. Heart attack symptoms vary among individuals,
and even a person who has had a previous heart attack may have different
symptoms in a subsequent heart attack. Although chest pain or pressure
is the most common symptom of a heart attack, heart attack victims may experience a
diversity of symptoms that include:
- Pain, fullness, and/or squeezing sensation of the
chest
- Jaw pain, toothache, headache
What is a heart attack?
A heart attack (also known as a myocardial infarction) is the death of heart muscle from the sudden blockage of a coronary artery by a blood clot. Coronary arteries are blood vessels that supply the heart muscle with blood and oxygen. Blockage of a coronary artery deprives the heart muscle of blood and oxygen,causing injury to the heart muscle. Injury to the heart muscle causes chest pain
and chest pressure sensation. If blood flow is not restored to the heart muscle within 20 to 40 minutes, irreversible death of the heart muscle will begin to occur. Muscle continues to
die for six to eight hours at which time the heart attack usually is "complete." The dead heart muscle is eventually replaced by scar tissue.
Approximately one million Americans suffer a heart attack each year. Four hundred thousand of them die as a result of their heart attack.
What causes a heart attack?
Atherosclerosis
Atherosclerosis is a gradual process by which plaques (collections) of cholesterol are deposited in the walls of arteries. Cholesterol plaques cause hardening of the arterial walls and narrowing of the inner channel (lumen) of the artery. Arteries that are narrowed by atherosclerosis cannot deliver enough blood to maintain normal function of the parts of the body they supply. For
example, atherosclerosis of the arteries in the legs causes reduced blood flow to the legs. Reduced blood flow to the legs can lead to pain in the legs while walking or exercising, leg ulcers, or a delay in the healing of wounds to the legs. Atherosclerosis of the arteries that furnish blood to the brain can lead to vascular dementia (mental deterioration due to gradual death of brain tissue over many years) or stroke (sudden death of brain tissue).
In many people, atherosclerosis can remain silent (causing no symptoms or
health problems) for years or decades. Atherosclerosis can begin as early as the
teenage years, but symptoms or health problems usually do not arise until later
in adulthood when the arterial narrowing becomes severe. Smoking cigarettes,
high blood pressure,
elevated cholesterol, and diabetes mellitus can accelerate
atherosclerosis and lead to the earlier onset of symptoms and complications,
particularly in those people who have a family history of early atherosclerosis.
Coronary atherosclerosis (or coronary artery disease) refers to the
atherosclerosis that causes hardening and narrowing of the coronary arteries.
Diseases caused by the reduced blood supply to the heart muscle from coronary
atherosclerosis are called coronary heart diseases (CHD). Coronary heart
diseases include heart attacks, sudden unexpected death, chest pain (angina),
abnormal heart rhythms, and heart failure due to weakening of the heart muscle.
Atherosclerosis and angina pectoris
Angina pectoris (also referred to as angina) is chest pain or pressure that
occurs when the blood and oxygen supply to the heart muscle cannot keep up with
the needs of the muscle. When coronary arteries are narrowed by more than 50 to
70 percent, the arteries may not be able to increase the supply of blood to the heart muscle during
exercise or other periods of high demand for oxygen. An insufficient supply of
oxygen to the heart muscle causes angina. Angina that occurs with exercise or
exertion is called exertional angina. In some patients, especially diabetics,
the progressive decrease in blood flow to the heart may occur without any pain
or with just shortness of breath or unusually early fatigue.
Exertional angina usually feels like a pressure, heaviness, squeezing, or
aching across the chest. This pain may travel to the neck, jaw, arms, back, or
even the teeth, and may be accompanied by shortness of breath, nausea, or a cold
sweat. Exertional angina typically lasts from one to 15 minutes and is relieved by
rest or by taking nitroglycerin
by placing a tablet under the tongue. Both resting and
nitroglycerin decrease the heart muscle's demand for oxygen, thus relieving
angina. Exertional angina may be the first warning sign of advanced coronary
artery disease. Chest pains that just last a few seconds rarely are due to
coronary artery disease.
Angina also can occur at rest. Angina at rest more commonly indicates that a coronary artery
has narrowed to such a critical degree that the heart is not
receiving enough oxygen even at rest. Angina at rest infrequently may be due
to spasm of a coronary artery (a condition called Prinzmetal's or variant angina).
Unlike a heart attack, there is no permanent muscle damage with either
exertional or rest angina.
Atherosclerosis and heart attack
Occasionally the surface of a cholesterol plaque in a coronary artery may
rupture, and a blood clot forms on the surface of the plaque. The clot blocks
the flow of blood through the artery and results in a heart attack (see
picture below). The cause of rupture that leads to the formation of a clot is largely
unknown, but contributing factors may include
cigarette smoking or other
nicotine exposure, elevated LDL cholesterol, elevated levels of blood
catecholamines (adrenaline), high blood pressure, and other mechanical and
biochemical forces.
Unlike exertional or rest angina, heart muscle dies during a heart attack
and loss of the muscle is permanent, unless blood flow can be promptly restored,
usually within one to six hours.
While heart attacks can occur at any time, more heart attacks occur between
4:00 A.M. and 10:00 A.M. because of the higher blood levels of adrenaline released
from the adrenal glands during the morning hours. Increased adrenaline, as
previously discussed, may contribute to rupture of cholesterol plaques.
Approximately 50% of patients who develop heart attacks have warning symptoms
such as exertional angina or rest angina prior to their heart attacks, but these
symptoms may be mild and discounted.
Next: What are the symptoms of a heart attack? »
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