Heart Attack
(Myocardial Infarction)
Medical Authors and Editors: Dennis Lee, MD and
Daniel
Kulick, MD, FACC, FSCAI
Revising Medical Editor: Jay Marks, MD
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Medical Emergency In Flight: Heartburn or Heart Attack?
(Words Of Caution From An Editor In Flight)
 This is a true story of an incident that occurred on an airline flight in
which the Chief Editor of MedicineNet.com was a passenger. The events of the flight present medical messages for all.
On a flight across country the recently, I had an experience that was exciting and fulfilling as a doctor and a passenger.
We left Newark, New Jersey at 7:20 am destined for Las Vegas. Just after the morning breakfast, I began to doze off into sleep. (My 2-day stay in New Jersey, from California, was work-filled.) Suddenly, my slumber was interrupted by the flight attendant's overhead anxious query, "Is there a medical professional aboard?"
I rushed to the back of the jet, stated that I was a doctor, and immediately was directed to the lavatory. There was a fully-clothed man, sitting on the closed toilet seat, slumped against the right wall. He was barely conscious, sweating, and had a slow, weak pulse. I explained to the man that I was a doctor and wanted to lay him down on the floor of the adjacent kitchen.
Slowly, he was able to assist in the transfer and I was able to lay him down gently onto pillows that the attendants had gathered. We applied oxygen and took a blood pressure reading that was relatively normal. His pulse rate, breathing, and strength became normal. His lethargy rapidly improved the longer he was lying down and he denied feeling any pain.
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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 pressure. If blood flow is not restored 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 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.
Click here
to view interactive photos of hearts that have suffered a heart attack.
What causes a heart attack?
Atherosclerosis
Atherosclerosis is a gradual process in 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 cannot 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 placing a nitroglycerin 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
diagram 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.
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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Last Editorial Review: 4/18/2007
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