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Is Coronary Artery Disease?
by Christopher Friedrich, MD,PhD and Andy Avins, MD
coronary arteries serve as
the main blood supply for the heart muscle, which requires
oxygen and other nutrients in order to function. Coronary
artery disease (CAD) occurs when these arteries become
narrowed or clogged. When the heart doesn't get enough
oxygen, the muscle becomes injured, which usually causes
chest pain called angina. If untreated, CAD can progress
to the point where the coronary arteries are completely
blocked, cutting off the heart's blood supply. This
is what is commonly known as a heart attack, or in medical
terminology, a myocardial infarction.
may have encountered the term coronary heart disease
(CHD), which occurs when CAD results in permanent damage
to the heart muscle. CHD and CAD are often used interchangeably;
here, we will use CAD as a blanket term for both conditions.
What Are Blood Vessels Made of?
vessels are tubes that transport blood throughout the
body. All blood vessels have an inner lining called
the endothelium, which is surrounded by connective tissue
and thin layers of muscle. Although these muscles are
not under our voluntary control, they play an important
role in determining blood pressure. The tone of these
muscles can be affected in the short term by exertion
or excitement, and in the long term by factors such
as smoking and diabetes.
is caused by a narrowing of coronary arteries, called
atherosclerosis. Blood flow becomes more and more restricted
as the artery continues to narrow.
commonly, atherosclerosis results when cholesterol and
fat circulating in the bloodstream build up on the artery
walls. The triggering event is an injury to the artery's
inner lining; the injury can be caused by high blood
or other causes. The body's immune
system responds to the injury,
causing inflammation. Immune cells called macrophages
are activated and try to heal the injury. This process
creates a plaque within the artery wall made up of low
density lipoprotein (LDL cholesterol), other fats, and
plaques are hard; others have just a thin cap on top
of a soft, fatty core. If the cap ruptures, the underlying
core will be exposed to the blood, triggering the formation
of a blood clot. If the blood clot is large enough,
blood flow in the artery will be completely blocked.
This is what causes a heart attack.
of CAD can range widely, from no symptoms at all, to
mild intermittent chest pain, to pronounced and steady
pain. In some people, symptoms can be severe enough
to hinder their normal daily activities. A person experiencing
angina may feel heaviness, tightness, pain, burning,
pressure, or squeezing, usually behind the breastbone
but sometimes also in the arms, neck, or jaws. These
sensations are usually localized to the left side of
the body. Angina is often accompanied by shortness of
breath, and sometime by nausea and sweating. These symptoms
are usually brought on by exertion and relieved by rest.
Nevertheless, some people (especially diabetics) have
heart attacks without ever experiencing any of these
to the American Heart Association, the most common warning
Uncomfortable pressure, fullness, squeezing, or pain
in the center of the chest that lasts more than a
few minutes, or goes away and comes back
Pain that spreads to the shoulders, neck or arms
discomfort with lightheadedness, fainting, sweating,
nausea, or shortness of breath
common warning signs include...
Any chest pain unlike the pain described above
Stomach or abdominal pain
Nausea or dizziness (without chest pain)
Shortness of breath and difficulty breathing (without
Unexplained anxiety, weakness, or fatigue
Palpitations, cold sweat, or paleness
all patients experiencing these symptoms have CAD. However,
if you experience these symptoms, you should consult
your doctor for further evaluation.
That Increase Risk
risk of developing CAD is a factor of both your genes and your environment. Studies of identical twins have revealed just how important it is to consider both genes and environment when assessing your risk of developing CAD. Even if you are genetically predisposed to develop CAD, a healthy lifestyle may allow you to live to old age without ever experiencing symptoms. Similarly, just because there is no CAD in your family doesn't guarantee that you won't develop it yourself. Most people develop CAD after the age of 45 (in men) or 55 (in women). However, your risk increases if you have a family member who had CAD before age 50, or if you have ever had chest pain, heart attack, stroke, or other vascular diseases. (
For news about environmental factors that increase risk, see Related News below.)
there is nothing you can do to change your family history
of CAD, you can control your environmental (nongenetic)
risk factors, including:
Smoking. The worst thing you can do for your
heart is smoke. The risk of heart attack is twice
as high for smokers as for nonsmokers, and smokers
who suffer a heart attack are more likely to die within
an hour of the attack. The good news is, no matter
how long or how much you've smoked, your risk of CAD
will rapidly decline as soon as you quit smoking.
It's never too late to stop smoking.
High cholesterol levels.
Higher cholesterol levels increase the risk of CAD
because cholesterol builds up on artery walls. Adults
over 35 years of age should have their cholesterol
levels measured at least once every five years. If
your parents developed CAD before age 50, you should
begin cholesterol screening earlier. Although there
is a genetic component to how much cholesterol is
in your blood, you can control it to some extent by
exercising regularly and eating a diet low in cholesterol
and saturated fat. If necessary, you can also take
medications to help manage your cholesterol.
High blood pressure can also increase your risk for
heart attack. Often blood pressure can be kept under
control by limiting salt intake, exercising regularly,
avoiding excessive alcohol intake, and maintaining
a healthy weight. For high blood pressure that doesn't
respond to these measures, medication can keep it
within healthy limits.
Click above to view weight index table
body mass index is used to assess a person's
body weight relative to height. It's a useful,
indirect measure of body composition, because
it correlates highly with body fat in most people.
People who are too heavy for their height more likely
to develop CAD, even with no other risk factors. This
is because extra weight increases blood pressure and
cholesterol, both of which are CAD risk factors.
Diabetes can make CAD worse in many different ways.
High blood glucose can cause elevated levels of blood
fats and cholesterol, promote injury to the inside
of blood vessels, and affect the immune system.
Most doctors believe that high levels of stress can
also increase the risk of CAD. This is difficult to
prove because there is no way to accurately measure
how much stress a person has, or even how stress affects
a person. However, research has indicated that managing
stress may profoundly reduce the risk of CAD.
these environmental risk factors increase every person's
chance of developing CAD, they put you at particular
risk if you also have family members with CAD.
You may want to pay special attention to genetic risk factors if:
- Other people in your family have developed CAD early in life (i.e., before age 45 in men or before age 55 in women)
- Multiple people in your family have or have had CAD
- A genetic syndrome or familial diagnosis has been identified in your family
Because symptoms can vary widely, there is no one simple test for CAD. Your doctor will always begin by taking a careful medical history and performing a thorough physical exam. The history and physical exam are extremely sensitive and specific tests for determining whether symptoms are due to CAD. If the history and physical exam suggest CAD, then your doctor may then use a combination of diagnostic procedures to measure the extent and severity of any CAD, and to rule out other possible causes of symptoms. (For recent news about screening, see Related News below.)
An electrocardiogram (ECG or EKG) records the
heart's electrical activity as it contracts and rests.
An EKG can detect abnormal heart beats, areas of heart
muscle damage, inadequate blood flow, and enlargement
of the heart.
stress test (also called a treadmill test)
can be useful because some problems only show up when
the heart is working hard and oxygen demands are higher.
In a stress test, an EKG is recorded before, during,
and after exercise. Another type of stress test employs
echocardiography during exercise to allow the doctor
to visualize how the heart performs under stress.
can identify regions of the heart in which blood flow
is limited. A small amount of radioactive material
is injected into a vein, usually in the arm. The amount
of nuclear material that is taken up by heart muscle
is then recorded using a scanning camera. Areas with
decreased blood flow will take up less radioactive
material than areas with normal blood flow.
(or coronary angiography) is the most definitive test
for CAD. A long, thin tube is inserted into a major
artery in leg or arm and then threaded all the way
into the coronary arteries. A special dye is injected
through this catheter and a series of x-rays are taken.
The dye is visible on the x-ray, so it is possible
to determine if a blockage is present and how serious
it is. This test allows doctors to see blockages in
the coronary arteries, but since it is more risky,
the other tests are usually performed first.
best bet is to prevent CAD before it starts. But even
after its onset, CAD can often be managed with a number
of lifestyle changes and medications. In more severe
cases, invasive interventions, such as surgery or balloon
angioplasty, may be required.
Stop smoking. If
you've recently been diagnosed with CAD and you smoke,
the most important thing is to stop smoking.
A healthy diet low in cholesterol and fat (especially
saturated fat) can help reduce blood cholesterol levels.
Studies have shown that extremely low-fat diets may
actually reverse the progress of CAD. Furthermore,
some oils, including fish oil and olive oil, may actually
be beneficial. And several studies have shown that
drinking red wine in moderation may also reduce your
risk. Eating less fat should also help you lose weight.
If you are overweight, losing weight can help reduce
high blood pressure, another risk factor for atherosclerosis
and heart disease.
Physical exercise is a great way to help lose
weight, lower blood pressure, and increase levels
of HDL (the "good" cholesterol). However, if you already
have CAD, be sure to check with your doctor before
beginning any exercise program.
can be prescribed to manage different aspects of CAD.
A variety of medications (beta-blockers, nitroglycerine,
and calcium channel blockers) can control symptoms
of angina. Aspirin reduces the tendency to form blood
clots. Cholesterol can be controlled using a variety
of medications, especially statins (HMG Co-A reductase
inhibitors). Medications can also be helpful for managing
high blood pressure.
For recent news about medications for CAD, see Related News below.
angioplasty can break open blockages in the coronary
arteries. A cardiologist inserts a catheter with a
tiny balloon at its tip through an arm or leg vein,
and then threads it into the coronary artery. The
balloon is inflated and deflated to improve the passage
for blood flow. The catheter is removed, but a device
called a "stent" is often inserted to keep the artery
bypass surgery is the most definitive treatment.
In this operation, a blood vessel taken from the leg
or chest is grafted onto the coronary artery, bypassing
the blockage. Depending on how many arteries are blocked,
surgeons may need to perform more than one bypass.
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