Unstable Angina (Acute Coronary Syndrome)

A. Pathophysiology and Symptoms
The pathophysiology of unstable angina has been
identified. In the majority of cases, disease-causing plaques
are asymmetric with irregular borders and a narrow neck.
Platelets then aggregate on the surface of plaques forming
small thrombi. Lipid-rich plaques have a predilection for
rupture, and rupture of the plaque with an overlying thrombus
is a common finding on angioscopy. Silent ischemia
is fatal and observed in patients with unstable angina.
Prognosis appears to be worse in this subset of patients.
Unstable angina patients represent a heterogeneous
group. Patients usually present with chest pain at rest
lasting from about 10 to 40 minutes; pain usually lasts
more than 20 minutes but less than hour. Patients with
stable angina with chest pain only on exertion who develop
pain with much lower levels of activities or pain at rest
are a subset of unstable angina. Patients with new onset
angina occurring within the past 30 days have high-risk
unstable angina.
B. Management
All patients with unstable angina should proceed to
an emergency room and be administered 160 mg of
chewable aspirin immediately if they have not already
taken the drug.
1. Risk Stratification and New Classification
During the past 50 years the three major complications
of CAD associated with chest pain were classified as
myocardial infarction, severe chest pain without elevated
cardiac enzymes classified as unstable angina, and chest
pain mainly on exertion labeled as chronic, stable angina.
For more information, see the chapter Heart Attacks.
Since 1998 national cardiac societies have altered this
classification as follows:
1. Patients with chest pain who have the characteristics of
a heart attack associated with typical ECG change
demonstrating ST-segment elevation are labeled as an
ST-segment elevation myocardial infarction (see the
chapter Heart Attacks).
2. Patients with chest pain and the characteristics of a
heart attack associated with ECG changes demonstrating
ST-segment depression accompanied by elevated
troponin or CK-MB enzyme elevations are labeled as
non-STelevation myocardial infarction (formerly called
non-Q-wave myocardial infarction).
Cardiac societies in the United States, Canada, and the
UK have introduced a new terminology: acute coronary
syndrome in an attempt to identify high risk patients with
acute chest pain. Classification of ischemic pain, acute
coronary syndrome includes:
1. Subset of patients with ST-segment elevation myocardial
infarction
2. Patients with non-ST elevation infarction (old term:
non-Q-wave MI)
3. Patients with typical features of unstable angina with
elevated troponin levels are reclassified as non-ST
elevation infarction
4. Patients with unstable angina: abnormal ECG changes
with normal troponin levels
5. Patients with unstable angina, normal ECG changes,
and normal troponins are classified as low risk
Patients are stratified into low- or high-risk categories
based on:
1. ECG changes done during pain showing ST-segment
depression indicating ischemic changes; ST-segment
depression greater than 0.05 mm (0.05 mV) indicates
high risk.
2. Patients with abnormal ECG and elevated troponins
are at high risk for serious events; elevated troponin
levels indicate necrosis of myocardial cells or a small
myocardial infarct.
3. Patients with evidence of recent onset of rest pain that is
recurrent, accompanied by ECG changes, are high risk.
4. Patients without rest pain and absence of ECG changes
with normal troponin levels are at low risk.
5. Diabetics with any of the above features are considered
high risk as are those patients who have had a previous
infarction.
6. An elevated C-reactive protein is considered to be
evidence of increased risk (see the chapter C-Reactive
Protein and the Heart).
2. Drug Management
Drug management is an important aspect of treating
unstable angina/acute coronary syndrome.
1. All patients are admitted to a coronary care unit or to
an area where telemetry and blood pressure monitoring
are available.
2. Intravenous nitroglycerin is given to virtually all
patients to relieve chest pain.
3. Morphine in small doses is given to stop pain that
can stimulate autonomic responses that may increase
cardiac arrhythmias and myocardial necrosis.
4. A beta-blocking drug is begun provided there is no
contraindication such as asthma or bradycardia less
than 50 beats per minute present.
5. Chewable aspirin is usually administered in the
emergency room followed by enteric-coated aspirin
325 mg once daily.
6. If A beta-blocking drug is contraindicated, a calcium
antagonist such as diltiazem is administered.
7. Heparin is given subcutaneously; low molecular
weight heparin has been shown to be equally as
effective as intravenous heparin and easier to monitor.
8. A statin is commenced to maintain LDL-cholesterol
levels less than 2.0 mmol/L (80 mg/dl).
9. Powerful antiplatelet agents are commenced, especially
in high-risk patients. Clopidogrel followed by catheterization
and coronary angiography are used to define
the lesion.
10. Glycoprotein IIb/IIIa receptor blockers such as:
abciximab (ReoPro), Integrilin, or tirofiban are
administered to high-risk patients undergoing coronary
angiography and/or angioplasty with or without
stent placement; several studies suggest that mainly
diabetics with acute coronary syndrome benefit
from such therapy. Abciximab has been shown to
have beneficial effects in randomized clinical trials
in acute coronary syndrome patients undergoing
angioplasty or stenting (see the chapter Antiplatelet
Agents).
3. Interventional Therapy
Interventional therapy such as coronary angioplasty with
or without stenting or bypass surgery should be strongly
considered in patients with high-risk unstable angina/acute
coronary syndrome. These patients usually undergo
coronary angiography within 24 h on admission to an
emergency room.
Coronary angiograms define the obstructive lesions, and
balloon angioplasty and stent placement are done in the
majority of patients. Balloon angioplasty with stenting has
transformed the management of unstable angina/acute
coronary syndrome (see the chapters Angioplasty and
Stents).
In most categories of patients and in virtually all
diabetics, interventional therapy has advantages over
medical therapy for amelioration of angina, a return to
normal lifestyle, and probable prolongation of life.
Coronary artery bypass surgery is indicated if angioplasty
or stenting are not possible, particularly in
patients with an ejection fraction of less than 45%,
and in diabetics.
When coronary artery bypass surgery is selected,
patients who can receive an internal mammary artery
graft are most fortunate. The arterial graft has a prolonged
patency of 15–20 years versus approximately 10–12 years
for saphenous vein grafts. Khot et al. have recently shown
that radial artery bypass grafts have an increased occurrence
of angiographically severe stenosis and occlusion
compared with left internal mammary artery grafts and
saphenous vein grafts (see the chapter Coronary Artery
Bypass Surgery).

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Variant Angina (Prinzmetal's Angina)

Prinzmetal’s variant angina is caused by coronary artery
spasm of undetermined etiology. Pain usually occurs at
rest as opposed to typical stable angina occurring during
exertion. The ECG during pain shows ST-segment
elevation as opposed to typical angina showing ST-segment
depression. An ECG is not necessary, however, to initiate
therapy.
Beta-blockers can increase coronary artery spasm
and cause chest pain so they are contraindicated in
these patients. Management includes cessation of smoking,
avoidance of aspirin that may cause spasm, and
the use of high doses of nitroglycerin and calcium
antagonists.
Unfortunately patients with variant angina, even when
the syndrome is completely controlled by calcium
antagonists, have died or have had myocardial infarctions.
Although calcium antagonists are efficient in controlling
the pain of coronary artery spasm, they do not prevent
death. Coronary artery bypass surgery is indicated in
patients with significant atheromatous coronary artery
obstruction, which occurs coincidentally in some patients
with variant angina.

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Silent Ischemia

Myocardial ischemia without pain or symptoms is
common in patients with CAD. The incidence of silent
ischemia is high and the outcome unfavorable in patients
with unstable angina. Interventional therapy is often
recommended. Holter monitoring after noncardiac surgery
in patients with stable angina and post myocardial
infarction patients has documented a high incidence of
silent ischemia within the second to fourth day after
surgery.
In the Total Ischemic Burden Bisoprolol Study, both
bisoprolol and nifedipine reduced the number and
duration of transient ischemic episodes. Bisoprolol was
significantly more effective than nifedipine and reduced
the morning peak of ischemic activity. This is in keeping
with other studies, which indicate that beta-blocking drugs
are superior to calcium antagonists in producing salutary
effects in patients with silent ischemia, especially in
reducing early morning ischemia that may relate to the
peak incidence of early morning heart attacks and death.
Patients with evidence of silent ischemia are recommended
to be treated with a beta-blocking drug, aspirin,
and a statin and investigated with exercise stress testing.
Those who show strongly positive exercise tests and/or
ejection fractions less than 45% should be submitted to
coronary angiography for consideration of an appropriate
revascularization procedure.

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Angina Patients With Heart Failure

Coronary artery disease leads to myocardial infarction
which causes weakness of the heart muscle, and some
patients over time develop heart failure. These patients
are difficult to treat because they are not candidates for
bypass surgery. Medical therapy must be used judiciously.
Nitrates, in particular cutaneous nitrates, applied 14 h
daily, plus a small dose of a beta-blocking drug along with
an ACE inhibitor and a diuretic, are beneficial for many
patients. Beta-blockers should be avoided in patients with
severe heart failure, but those with mild-to-moderate heart
failure gain major relief. Recent randomized clinical trials
have shown the beta-blockers, carvedilol, metoprolol, and
bisoprolol effective in reducing mortality rates and
hospitalization.
In patients with an ejection fraction less than 35%,
digoxin is indicated. Calcium antagonists should be
avoided. Verapamil and diltiazem are contraindicated
because of reduced cardiac contractility and the possibility
of precipitating heart failure. Other calcium antagonists
including amlodipine and nifedipine should be avoided
because they may precipitate heart failure

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Nondrug Treatment For Angina

NONDRUG TREATMENT
A. Weight Reduction Effects
If you have angina and you lose 10–25 lb, you will
certainly experience less pain, you will require a smaller
dose of antianginal medication, and you may not require
angioplasty or surgery.
Weight reduction, relief of stress, a low-saturated fat
diet, and avoidance of smoking are the most important
nondrug treatments for patients with angina. Weight loss
depends on eating less calories and burning off more
calories during exercise. A combination of a low-calorie
diet with some form of exercise program that increases
caloric expenditure must be followed, otherwise the
weight gain that often occurs after stopping a low-calorie
diet will ensue. All diets that are proven to cause weight
loss over a period of years depend on reduced intake of
calories. Calories do count, do not let anyone tell you
otherwise.
Weight loss occurs with reduction of calorie intake to
less than 1000 calories daily and exercise to burn off more
calories. A meal should contain a moderate amount of
protein, but a low-saturated fat content. Reduce your
intake of high-calorie foods containing refined sugars or
starches. A greater than 75% decrease in the usual
consumption of all products derived from wheat flour,
potatoes, and rice along with 40 minutes of exercise daily is
guaranteed to cause significant weight loss.
Fish three times weekly, even canned tuna, salmon,
sardines, and herring, will help to reduce the saturated fat
in the diet. Many individuals may stick to these rules, but
forget that alcohol, both mixes and beer, are high in
calories. Avoid fast foods because they often high in
calories and salt. An increase in salt increases the work of
the heart muscle and puts a strain on the heart, which can
lead to heart failure and shortness of breath. Thus, patients
with high blood pressure, heart failure, and angina are
advised to follow a low-salt diet.
Lack of motivation often results in a failure to reduce
weight. It is a tough battle for most overweight individuals
to fight on their own, and success is more often obtained
by joining a weight-loss program or clinic. We strongly
advise you to consult your physician or to contact your
Heart and Stroke Association for recommended publications
on weight loss. The Mediterranean style diet is
cardioprotective and strongly recommended, see chapters
Diets and Heart Disease and Dyslipidemia.
B. Exercise
What about exercise and angina? An exercise stress test
using a treadmill or bicycle under the supervision of a
physician should provide the answer to the question:
‘‘How much exercise is safe for me?’’ Usually, a safe level of
exercise is that which will bring on only mild discomfort or
mild shortness of breath. You should slow down for a few
seconds then stop for a minute or so before continuing the
activity (such as a quarter- or half-mile walk). Stretching
exercises and walking — including climbing two or three
flights of stairs daily — will improve your muscle tone.
Exercise alone, however, cannot remove the obstruction
caused by plaques in arteries. Patients with angina do not
jog because this activity often precipitates pain. For more
information, see the chapter Exercise and the Heart.
C. Smoking
Nonsmoking men are 10 times less likely to have a fatal or
nonfatal heart attack than heavy smokers. Sudden death
by heart attack is more common in heavy smokers than
in nonsmokers. Drugs that are effective in preventing
angina and death lose their effectiveness in smokers
because the by-products of cigarettes interfere with the
breakdown of the drugs in the liver. These drugs include
the frequently used beta-blocker propranolol and calcium
antagonists such as nifedipine. Also, bypass grafts become
blocked within a few years of bypass surgery in patients
who continue to smoke. If you have angina and chronic
bronchitis, cigarette smoking will cause an increase in
shortness of breath.
Women between the ages of 35 and 50 who have
functioning ovaries rarely suffer from angina or have heart
attacks. Women who smoke and have an elevated blood
cholesterol level, unfortunately, increase their risk of having
a heart attack and angina prior to age 50.
Perhaps, rather than quitting, changing to a different
brand of cigarettes is considered. The bad news is that
filter cigarettes and low-nicotine or low-tar brands of
cigarettes do not decrease the risk of heart attacks. In fact,
filter cigarettes deliver more carbon monoxide to the
smoker’s system and cause more heart attacks than plain
cigarettes.
The oxygen supply to the heart muscle is low in patients
with angina. Angina patients who are smokers experience
pain at lower levels of exercise. Nicotine causes a slight
increase in the heart rate and a rise in blood pressure;
therefore, the heart muscle demands more oxygen. Carbon
monoxide delivered from cigarettes steals oxygen away
from the heart muscle, which is already deprived of
oxygen. So the combination of carbon monoxide and
nicotine is bad news. Regardless of the present condition
of your heart, do yourself a favor and quit smoking.
Still, how do you stop smoking? It is easier said than
done. The first step is motivation. Consider the facts. The
dangers of carbon monoxide are well known. You wouldn’t
stand around inhaling exhaust fumes from a car, especially
if its engine was running in an enclosed garage; you
know that that situation would cause death. Yet, we have
information today that proves heavy cigarette smokers are
exposed to eight times the level of carbon monoxide
considered safe in industry, and it has been proven that
heavy cigarette smoking is a cause of heart attacks and
sudden death.
The addiction to nicotine is so powerful that nothing
will help if the smoker is not motivated to quit. Even
bronchitic patients continue to smoke because the addiction
to nicotine is so great. To help you to quit smoking,
enlist the assistance of stop smoking clinics; even hypnosis
is a viable alternative. The American Cancer Society and
the National Cancer Institute provide several types of
programs to help smokers quit. Local cancer societies
usually provide a list of programs that can help. Consult
a physician for advice on nicotine tablets, patch, gum,
or nasal spray. Most smokers who cannot motivate
themselves. Get help now!

D. L-Arginine
Arginine increases nitric oxide availability in the arterial
wall and this causes vasodilation and increases blood flow.
Some clinical trials indicate modest improvement in
angina symptoms with its use, but they are not consistent.
Arginine is found in many foods and an arginine food bar
is also available.



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Diagnosis Of Angina

Pain Pattern
1. Location
The pain of angina is usually felt in the center of the chest
over the breastbone, and only rarely over the breasts. Pain in the lower jaw
accompanied by pain in the chest or arms during a walk or
strenuous activity is nearly always due to angina, especially
if these symptoms recur during similar activities.
Sometimes the discomfort is only in the upper arm with a
tingling feeling in the fingers; this pain comes mainly
on exertion as opposed to pain produced, for example,
by a pinched nerve. A pinched nerve will cause similar
discomfort in the arms and fingers when the individual
is at rest, but an activity, such as walking, makes little
difference.
2. Severity and Character
The pain of angina may be mild to moderate and only
occasionally severe. Often it is just discomfort. The
individual may even refuse to use the word pain to describe
the peculiar sensation that feels like a tightness or a
heavy weight on the breastbone. To some it is a burning
sensation; to others it is a feeling of strangulation or
suffocation that fortunately disappears within one to five
minutes of rest, either with the individual standing or
sitting. The pain of angina rarely lasts more than 10
minutes. If an individual has pain similar to that described
and lasts more than 15 minutes, the patient should take
two or three soft, chewable aspirins (80 mg each) and go
immediately to a hospital emergency room.
Activities that Precipitate Angina
These precipitating activities include:
1. Walking up a hill
2. Walking against the wind
3. Running with some associated anxiety for a bus or to a
place, especially while carrying a bag; anxiety is made
more profound if the individual is late and must rush,
thus, there is exertion and emotional stress
4. A brisk walk or similar exertion soon after eating; this
does not include bending and stooping, which can
precipitate indigestion
5. Unaccustomed exertion
6. Emotional distress; for example, bad news, a scare,
anger, rage, nightmares, etc.
7. Pain may occur during overwhelming excitement; for
example, watching your team playing football, hockey,
baseball, basketball, and similar exciting programs
Most important, relief of pain in an individual with
stable angina always occurs within minutes of cessation of
the precipitating exertional or emotional activity. Relief
with nitroglycerin occurs promptly within one to two
minutes.

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