Download Atrial Fibrillation

Electrocardiogram
Atrial Fibrillation and Atrial
Flutter
 Atrial
fibrillation and atrial flutter are very
fast electrical discharge patterns that make
the atria contract very rapidly, with some of
the electrical impulses reaching the
ventricles and causing them to contract
faster and less efficiently than normal.
 Atrial fibrillation and atrial flutter are more
common among older people.
Pathogeny

Atrial fibrillation and atrial flutter may be intermittent or
sustained.

During atrial fibrillation or flutter, the contractions of the atria
are so fast that the atrial walls quiver. As a result, blood is not
pumped effectively to the ventricles.

During atrial fibrillation, the atrial rhythm is irregular, so the
ventricular rhythm is also irregular.
Pathogeny
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During atrial flutter, the atrial rhythm is regular, and the
ventricular rhythm may be regular or irregular.
In both cases, the ventricles beat more slowly than the atria
because the atrioventricular node cannot conduct electrical
impulses at such a fast rate. As a result, only some
impulses get through.
Even though the ventricles beat more slowly than the atria,
the ventricles often still beat too fast to fill completely.
Therefore, the heart pumps inefficiently, blood pressure
may fall, and heart failure may occur.
Atrial Fibrillation


An ECG strip shows the
presence of atrial fibrillation,
which involves rapid
uncoordinated contraction of
the atria.
Atrial fibrillation is indicated
by a very rapid (350 to 450
beats per minute) rate and an
erratic rhythm. The
ventricular (QRS) rate is
normal. A normal ECG strip is
shown at the bottom for
comparison
Atrial Flutter

An ECG strip shows the
presence of atrial flutter,
which involves rapid
uncoordinated
contraction of the atria.
Atrial flutter is indicated
by a very rapid (250 to
350 beats per minute)
rate and a ?saw tooth?
pattern. In this case, the
ventricular (QRS) rate is
also fast. A normal ECG
strip is shown at the
bottom for comparison
Pathogeny
In atrial fibrillation or flutter, the atria do not empty
completely into the ventricles with each beat.
 Over time, some blood inside the atria may stagnate,
and clots may form.
 Pieces of the clot may break off, often shortly after
atrial fibrillation converts back to normal rhythm—
whether spontaneously or because of treatment.
 These pieces may pass into the left ventricle, travel
through the bloodstream (becoming emboli), and block
a smaller artery.
 If pieces of a clot block an artery in the brain, a stroke
results. Rarely, a stroke is the first sign of atrial
fibrillation or flutter.

Pathogeny
Atrial fibrillation or flutter may occur even when
there is no other sign of heart disease. But, more often,
these arrhythmias are caused by such conditions as
rheumatic fever, high blood pressure, coronary artery
disease, alcohol abuse, an overactive thyroid gland
(hyperthyroidism), or a birth defect of the heart.
 Rheumatic fever (which leads to heart valve disorders)
and high blood pressure cause the atria to enlarge,
making atrial fibrillation or flutter more likely.

Symptoms and Diagnosis

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Symptoms of atrial fibrillation or flutter depend largely on how
fast the ventricles beat. A modest increase in the ventricular
rate—to less than about 120 beats per minute—may produce no
symptoms. Higher rates cause unpleasant palpitations or chest
discomfort.
In people with atrial fibrillation, the pulse is irregular and
usually fast. In people with atrial flutter, the pulse is more likely
to be regular and fast.
The reduced pumping ability of the heart may cause weakness,
faintness, and shortness of breath. Some people, especially older
people, develop heart failure or chest pain. Very rarely, shock
(very low blood pressure) occurs in people who have atrial
fibrillation or flutter and very severe heart disease.
Symptoms suggest the diagnosis of atrial fibrillation or flutter,
and electrocardiography (ECG) confirms it.
Treatment
Treatment of atrial fibrillation or flutter is designed
to:
 control the rate at which the ventricles contract
 restore the normal rhythm of the heart
 treat the disorder causing the arrhythmia
Drugs to prevent the formation of clots and emboli
(anticoagulants) may also be given.
Treatment

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Usually, the first step in treating atrial fibrillation or flutter is to
slow the beating of the ventricles so that the heart pumps blood
more efficiently.
Often, the first drug tried is digoxin (LANOXIN), which may
slow the conduction of impulses to the ventricles.
But, digoxin (LANOXIN) is often insufficient.
Another drug may be required. A beta-blocker, such as
propranolol
(INDERAL) or atenolol (TENORMIN), or
a calcium channel blocker, such as verapamil (CALAN,
ISOPTIN), or diltiazem (CARDIZEM, DILACOR), may be
used.
Treatment
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Atrial fibrillation or flutter may spontaneously convert to a
normal rhythm. But, these arrhythmias must often be actively
converted to normal.
Certain antiarrhythmic drugs (most commonly, amiodarone
CORDARONE), propafenone (RYTHMOL), or sotalol
(BETAPACE)
may be effective.
But cardioversion, or defibrillation (delivery of an electrical
shock to the heart), is the most effective approach.
Conversion to a normal rhythm by any means becomes less likely
the longer the arrhythmia has been present (especially after 6
months or more), the larger the atria become, and the more severe
the underlying heart disease becomes.
When conversion is successful, the risk of recurrence is high,
even if people are taking a drug to prevent recurrence (that is, one
of the drugs used to convert the arrhythmia to a normal rhythm).
Treatment
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Rarely, when all other treatments of atrial fibrillation are
ineffective, parts of the atrioventricular node can be destroyed
by radiofrequency ablation (delivery of energy of a specific
frequency through an electrode catheter inserted in the heart).
This procedure slows the ventricular rate in some people who
have atrial fibrillation or flutter.
If this procedure is not successful, radiofrequency ablation is
used to destroy the entire atrioventricular node, completely
stopping conduction from the atria to the ventricles.
In such cases, a permanent artificial pacemaker is required to
activate the ventricles afterward. For people who have atrial
flutter, radiofrequency ablation may be used to interrupt the
flutter circuit and permanently re-establish normal rhythm. This
procedure is successful in about 85% of people.
Treatment
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Usually, treatment of the underlying disorder does not alleviate
atrial arrhythmias. But, treatment of an overactive thyroid gland
or surgery to correct a heart valve disorder or a birth defect of
the heart may help.
When atrial fibrillation or flutter is converted back to normal
rhythm, the risk that a clot will be dislodged and cause a stroke
is particularly high.
Most people with atrial fibrillation or flutter and one or more
risk factors for developing clots are given an anticoagulant to
prevent clots, because they are at risk of a stroke.
Risk factors for developing blood clots include advancing age,
high blood pressure, diabetes, an enlarged left atrium, and
structural heart disease, especially mitral valve disorders.
Treatment
Unless conversion to a normal rhythm is needed
immediately, doctors recommend that most people take
an anticoagulant for 4 weeks before cardioversion of
established atrial fibrillation or flutter is attempted.
 But, sometimes there is a specific reason not to use an
anticoagulant. People who have uncontrolled high
blood pressure or a bleeding disorder should not be
given anticoagulants.
 Anticoagulant therapy can cause bleeding, which can
lead to hemorrhagic stroke and other bleeding
complications, such as excessive bleeding after surgery.
 Therefore, doctors balance the potential benefits and
risks for each person.

Atrial Premature Beats
An atrial premature beat (atrial ectopic beat,
premature atrial contraction) is an extra
heartbeat caused by electrical activation of the
atria from an abnormal site before a normal
heartbeat would occur.
Causes
Atrial premature beats occur in many
healthy people and rarely cause symptoms.
 Atrial premature beats are common among
people who have lung disorders and are
more common among older people than
among younger people.
 These beats may be caused or worsened by
consuming coffee, tea, or alcohol and by
using some cold, hay fever, and asthma
remedies.
ECG: Atrial Ectopic Beats

An ECG strip shows the
presence of atrial ectopic
beats, which are
heartbeats that occur in
addition to a normal
heartbeat. Atrial ectopic
beats are seen as small
spikes (P) in a continuous
pattern of larger spikes
and waves. A normal
ECG strip is shown at the
bottom for comparison.
Diagnosis and Treatment
 Atrial
premature beats may be detected during
a physical examination and are confirmed by
electrocardiography (ECG).
 Rarely, when these beats occur frequently and
cause intolerable palpitations, treatment is
necessary.
 Antiarrhythmic drugs are usually effective.
Paroxysmal Supraventricular
Tachycardia
Paroxysmal supraventricular (atrial)
tachycardia is a regular, fast (160 to 200
beats per minute) heart rate that begins and
ends suddenly and originates in heart tissue
other than that in the ventricles.
Causes
 Paroxysmal
supraventricular tachycardia is
most common among young people and is more
unpleasant than dangerous. It may occur during
vigorous exercise.
 Paroxysmal supraventricular tachycardia
may be triggered by a premature heartbeat that
repeatedly activates the heart at a fast rate. This
repeated, rapid activation may be caused by
several abnormalities.
Causes
There may be two electrical pathways in the
atrioventricular node (an arrhythmia called
atrioventricular nodal reentrant supraventricular
tachycardia). There may be an abnormal electrical
pathway between the atria and the ventricles (an
arrhythmia called atrioventricular reciprocating
supraventricular tachycardia).
 Much less commonly, the atria may generate
abnormal rapid or circling impulses (an
arrhythmia called true paroxysmal atrial
tachycardia).

Symptoms
 The fast heart rate tends to begin and end
suddenly and may last from a few minutes to
many hours.
 It is almost always experienced as an
uncomfortable palpitation.
 It is often associated with other symptoms, such as
weakness, light-headedness, shortness of breath,
and chest pain.
 Usually, the heart is otherwise normal.
ECG: Paroxysmal Atrial
Tachycardia
An ECG strip shows the
presence of paroxysmal
atrial tachycardia, which
is one type of rapid
heartbeat. Paroxysmal
atrial tachycardia is
indicated by a very
rapid but otherwise
normal ECG rhythm. A
normal ECG strip is
shown at the bottom for
comparison.
Treatment
Episodes of paroxysmal supraventricular tachycardia often can
be stopped by one of several maneuvers that stimulate the
vagus nerve and thus decrease the heart rate.
 These maneuvers are usually conducted or supervised by a
doctor, but people who repeatedly experience the arrhythmia
often learn to perform the maneuvers themselves.
 Maneuvers include:
- straining as if having a difficult bowel movement
- rubbing the neck just below the angle of the jaw (which
stimulates a sensitive area on the carotid artery called the
carotid sinus)
- plunging the face into a bowl of ice-cold water.
These maneuvers are most effective when they are used shortly
after the arrhythmia starts.

Treatment
 If
these maneuvers are not effective, if the
arrhythmia produces severe symptoms, or if the
episode lasts more than 20 minutes, people are
advised to seek medical intervention to stop the
episode.
 Doctors can usually stop an episode promptly by
giving an intravenous injection of a drug, usually
adenosine (ADENOCARD),
or verapamil(CALAN ISOPTIN).
 Rarely, drugs are ineffective, and cardioversion
(delivery of an electrical shock to the heart) may
be necessary.
Treatment
Prevention is more difficult than treatment, but almost
any antiarrhythmic drug may be effective. Drugs
commonly used include beta-blockers, digoxin,
diltiazem (CARDIZEM, DILACOR) , verapamil
(CALAN, ISOPTIN), propafenone (RYTHMOL), and
flecainide (TAMBOCOR).
 Increasingly, radiofrequency ablation (delivery of
energy of a specific frequency through an electrode
catheter inserted in the heart) is being used to destroy
the tissue in which paroxysmal supraventricular
tachycardia originates.

Ventricular Fibrillation
 Ventricular
fibrillation is a potentially
fatal, uncoordinated series of very rapid,
ineffective contractions of the ventricles
caused by many chaotic electrical impulses.
 In ventricular fibrillation, the ventricles
merely quiver and do not contract in a
coordinated way. No blood is pumped from
the heart, so ventricular fibrillation is a form
of cardiac arrest. It is fatal unless treated
immediately.
Causes
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The most common cause of ventricular fibrillation is
inadequate blood flow to the heart muscle due to coronary
artery disease, as occurs during a heart attack.
Other causes include shock (very low blood pressure),
which can result from:
coronary artery disease and other disorders;
electrical shock;
drowning;
very low levels of potassium in the blood (hypokalemia);
drugs that affect electrical currents in the heart (such as
sodium or potassium channel blockers
ECG: Ventricular Fibrillation
An ECG strip shows the
presence of ventricular
fibrillation, which
involves rapid
contraction of the
ventricles. Ventricular
fibrillation is indicated
by an erratic rhythm in
which spikes and waves
cannot be identified. A
normal ECG strip is
shown at the bottom for
comparison.
Symptoms and Diagnosis
Ventricular fibrillation causes unconsciousness
in seconds. If untreated, the person usually has
seizures and develops irreversible brain damage
after about 5 minutes because oxygen no longer
reaches the brain. Death soon follows.
 Cardiac arrest is diagnosed when a person
suddenly collapses, turns deadly white, has very
dilated pupils, and has no detectable pulse,
heartbeat, or blood pressure.
 Ventricular fibrillation is diagnosed as the cause of
the cardiac arrest by electrocardiography (ECG).

Treatment
 Ventricular
fibrillation must be treated as
an extreme emergency. Cardiopulmonary
resuscitation (CPR) must be started as soon
as possible—within a few minutes. It must
be followed by cardioversion, or
defibrillation (an electrical shock delivered
to the chest), as soon as the defibrillator is
available.
 Antiarrhythmic drugs may then be given
to help maintain the normal heart rhythm.
Treatment
When ventricular fibrillation occurs within a few
hours of a heart attack in people who are not in
shock and who do not have heart failure, prompt
cardioversion restores normal rhythm in 95% of
people, and the prognosis is good.
 Shock and heart failure suggest major damage to
the ventricles. If they are present, even prompt
cardioversion has only a 30% success rate, and
70% of resuscitated survivors die without
regaining normal function.

Treatment
 People
who are successfully resuscitated
from ventricular fibrillation and survive are
at high risk of another episode.
 If ventricular fibrillation is caused by a
reversible disorder, that disorder is treated.
 Otherwise, drugs are given to prevent
recurrences, or a defibrillator is surgically
implanted to correct the problem, if it
recurs, by delivering a shock.
Ventricular Premature Beats
A ventricular premature beat (ventricular
ectopic beat, premature ventricular
contraction) is an extra heartbeat resulting
from abnormal electrical activation
originating in the ventricles before a normal
heartbeat would occur.
Causes

Ventricular premature beats are common,
particularly among older people. This arrhythmia
may be caused by physical or emotional stress,
intake of caffeine (in beverages and foods) or
alcohol, or use of cold or hay fever remedies
containing drugs that stimulate the heart, such as
pseudoephedrine (AFRINOL, SUDAFED)

Other causes include coronary artery disease
(especially during or shortly after a heart attack)
and disorders that cause ventricles to enlarge, such
as heart failure and heart valve disorders.
ECG: Ventricular Ectopic
Beats
An ECG strip shows the
presence of ventricular
ectopic beats, which are
heartbeats that occur in
addition to a normal
heartbeat. Ventricular
ectopic beats are seen as
large, wide spikes among a
pattern of thinner, normal
QRS spikes. A normal ECG
strip is shown at the bottom
for comparison.
Symptoms and Diagnosis

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Isolated ventricular premature beats have little effect on the
pumping action of the heart and usually do not cause
symptoms, unless they are extremely frequent.
The main symptom is the perception of a strong or skipped
beat. Ventricular premature beats are not dangerous for
people who do not have heart disease. But, when they
occur frequently in people who have structural heart
disease, they may be followed by more dangerous
arrhythmias such as ventricular tachycardia or ventricular
fibrillation, which can cause sudden death.
Electrocardiography (ECG) is used to diagnose ventricular
premature beats.
Treatment
In an otherwise healthy person, no treatment is needed
other than decreasing stress and avoiding caffeine,
alcohol, and over-the-counter cold or hay fever
remedies containing drugs that stimulate the heart.
 Drug therapy is usually prescribed only if symptoms
are intolerable or if the pattern of ventricular
premature beats suggests a risk of progression to
ventricular tachycardia or ventricular fibrillation.
 The presence of structural heart disease or runs of
consecutive ventricular beats suggest this risk.
 Beta-blockers are usually tried first because they are
relatively safe drugs. But, some people do not want to
take them because they can cause sluggishness.

Treatment
After a heart attack, people who have frequent
ventricular premature beats may reduce the risk of
sudden death due to ventricular tachycardia or
ventricular fibrillation by taking beta-blockers or
undergoing angioplasty or coronary artery
bypass surgery to treat coronary artery disease.
 Antiarrhythmic drugs can suppress ventricular
premature beats, but they also may increase the
risk of a fatal arrhythmia.
 Therefore, doctors prescribe them only for
carefully selected people who have been evaluated
for risk of developing serious arrhythmias.

Ventricular Tachycardia
Ventricular tachycardia is a heart rhythm
that originates in the ventricles and
produces a heart rate of at least 120 beats
per minute.
Causes
Ventricular tachycardia may be thought of as a
sequence of consecutive ventricular premature beats.
Sometimes only a few such beats occur together, and
then the heart returns to a normal rhythm.
 Ventricular tachycardia that lasts more than 30
seconds is called sustained ventricular
tachycardia. Sustained ventricular tachycardia
usually occurs in people with structural heart disease
that damages the ventricles. Most commonly, it
occurs weeks or months after a heart attack.
 It is more common among older people. But, rarely,
ventricular tachycardia develops in young people
who do not have structural heart disease.

ECG: Ventricular Tachycardia

An ECG strip shows
the presence of
ventricular tachycardia,
which is one type of a
rapid heartbeat.
Ventricular tachycardia
is indicated by a series
of repeating wide
uncoordinated spikes.
A normal ECG strip is
shown at the bottom
for comparison.
Symptoms and Diagnosis
People with almost always have palpitations. Sustained
ventricular tachycardia can be dangerous because the
ventricles cannot fill adequately or pump blood normally.
 Blood pressure tends to fall, and heart failure follows.
 Sustained ventricular tachycardia is also dangerous
because it can worsen until it becomes ventricular
fibrillation—a form of cardiac arrest.
 Sometimes ventricular tachycardia causes few symptoms,
even at rates of up to 200 beats per minute, but it may still
be extremely dangerous.

Symptoms and Diagnosis
Electrocardiography (ECG) is used to diagnose
ventricular tachycardia and to help determine
whether treatment is required.
 A portable ECG (Holter) monitor may be used to
record heart rhythm over a 24-hour period.

Treatment
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Ventricular tachycardia is treated when it causes symptoms or
when episodes last more than 30 seconds even without causing
symptoms.
Sustained ventricular tachycardia often requires emergency
treatment.
If episodes cause blood pressure to fall to a low level,
cardioversion is needed immediately.
Drugs may be given intravenously to end or suppress ventricular
tachycardia.
The most commonly used drugs are lidocaine, procainamide
(PROCAN SR, PRONESTYL), and
amiodarone (CORDARONE)
Treatment
Certain procedures may be performed to destroy the
small abnormal area in the ventricles, identified by
ECG, that is usually responsible for sustained
ventricular tachycardia. They include radiofrequency
ablation (delivery of energy of a specific frequency
through an electrode catheter inserted in the heart) and
open-heart surgery.
 If other therapy is ineffective, an automatic
defibrillator (a small device that can detect an
arrhythmia and deliver a shock to correct it) may be
implanted. This procedure is similar to implantation of
an artificial pacemaker.

Heart Block
Heart block is a delay in the conduction of
electrical current as it passes through the
atrioventricular node, bundle of His, or
both bundle branches, all of which are
located between the atria and the ventricles.
ECG: Heart Block

An ECG strip shows the
presence of heart block,
in which conduction of
the heartbeat from the
atria to the ventricles is
delayed. Heart block may
be indicated by a delay in
the spikes that
progressively increases. A
normal ECG strip is
shown at the bottom for
comparison
Classification
Heart block is classified as first-degree when
electrical conduction to the ventricles is slightly
delayed.
 Second-degree when conduction is intermittently
blocked.
 Third-degree (complete) when conduction is
completely blocked.

Most types of heart block are more common
among older people.
First-degree heart block
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In first-degree heart block, every electrical impulse from the atria
reaches the ventricles, but each is slowed for a fraction of a
second as it moves through the atrioventricular node.
First-degree heart block is common among well-trained athletes,
teenagers, young adults, and people with a highly active vagus
nerve. But, the disorder also occurs in people with rheumatic
fever, sarcoidosis that affects the heart, or other structural heart
diseases.
It may be caused by drugs, particularly those that slow
conduction of electrical impulses through the atrioventricular
node (such as beta-blockers, diltiazem (CARDIZEM,
DILACOR), verapamil (CALAN, ISOPTIN), and amiodarone
(CORDARONE).
This disorder produces no symptoms and can be detected only by
electrocardiography (ECG), which shows the conduction delay.
Second-degree heart block
 In
second-degree heart block, only some
electrical impulses reach the ventricles.
 The heart may beat slowly, irregularly, or
both.
 Some forms of second-degree heart block
progress to third-degree heart block.
Third-degree heart block
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In third-degree heart block, no impulses from the atria reach the
ventricles, and the ventricular rate and rhythm are controlled by
the atrioventricular node, bundle of His, or the ventricles
themselves.
These substitute pacemakers are slower than the heart's normal
pacemaker (sinus or sinoatrial node) and are often irregular and
unreliable.
Thus, the ventricles beat very slowly—less than 50 beats per
minute and sometimes as slowly as 30 beats per minute.
Third-degree heart block is a serious arrhythmia that can affect
the heart's pumping ability. Fatigue, dizziness, and fainting are
common. When the ventricles beat faster than 40 beats per
minute, symptoms are less severe.
Treatment
First-degree heart block requires no treatment even
when it is caused by heart disease.
 Some people with second-degree heart block require
an artificial pacemaker.
 Almost all people with third-degree heart block
require an artificial pacemaker. A temporary pacemaker
may be used in an emergency until a permanent one can
be implanted.
 Most people need an artificial pacemaker for the rest of
their lives, although heart rhythm may return to normal
if the cause of the heart block resolves—after recovery
from a heart attack.

Bundle Branch Block
Bundle branch block is a type of
conduction block involving partial or
complete interruption of the flow of
electrical impulses through the right or left
bundle branches.
Bundle Branch Block
 The
bundle of His is a group of fibers that
conducts electrical impulses from the
atrioventricular node.
 The bundle of His divides into two bundle
branches.
 The left bundle branch conducts impulses to
the left ventricle, and the right bundle branch
conducts impulses to the right ventricle.
 Conduction may be blocked in the left or right
bundle branch.
Bundle Branch Block
Bundle branch block usually causes no symptoms.
 Right bundle branch block is not serious in itself
and may occur in apparently healthy people. But,
it may also indicate significant heart damage due
to, for example, a previous heart attack.
 Left bundle branch block tends to be more
serious. In older people, it often indicates heart
disease due to high blood pressure or
atherosclerosis.

Bundle Branch Block
Bundle branch block can be detected by
electrocardiography (ECG).
 Each type of block produces a characteristic
pattern.
 Usually, no treatment is needed for either type.
 But, an artificial pacemaker may be implanted in
people who are at high risk of complete heart
block (such as people with second-degree heart
block) to maintain the heart rate if complete heart
block occurs.
