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number of times the heart beats each minute (BPM) is called the heart
rate. The time from one beat to the next is about the same. The
resting heart rate for a newborn is about 140 BPM, that for an older
child or adolescent 70-80 BPM, and 60-70 BPM for an adult.
The heart rate can easily change. For example, exercise makes the heart
speed up; during sleep it slows down. Arrhythmia's, specialized tests
and treatments are discussed below.
the heart isn't beating regularly, it has an arrhythmia.
The most common, but normal, heart rhythm irregularity occurs during
breathing. When a person breathes in, the heart rate normally speeds
up for a few beats. It slows down again when a person breaths out. This
variation with breathing is called sinus
arrhythmia and is completely normal. A doctor may find irregularities
that differ from a sinus arrhythmia. The heart may seem to skip a beat
or beat irregularly or very fast or very slowly. Then the doctor may
want to perform other tests or may recommend that the patient be seen
by a cardiologist (a doctor who specializes in heart problems).
can occur at any age, even in infants. They commonly in middle-age adults.
As people get older, they are more likely to experience an arrhythmia.
happens in the heart during an arrhythmia?
normal heart is a strong, hardworking, muscular pump. A person's heart,
when normal sized, is slightly larger than his or her fist. Describing
how the heart beats normally helps to explain what happens during an
heart is divided into right and left sides; there's an upper and lower
chamber on each side. The right and left atria
(upper chambers) receive blood from the body and the lungs. The right
and left ventricles (lower chambers) are the
muscular chambers. They pump blood out of the heart to the lungs and
blood travels through the heart, it moves through a series of valves.
The valves open and close to let blood flow in only one direction.
animated pumping heart )
Each heartbeat begins when a specialized area of the right atrium (the
sinus node or S-A node, which is also called the heart's pacemaker)
generates a small amount of electricity. Each electrical signal leaves
the sinus node and spreads into the muscle cells of the heart's atria.
This causes them to contract (beat).
electrical activity then moves into the junction between the atria
and ventricles. There it passes through the atrioventricular
node (A-V node). The A-V node acts as a relay station. It takes
the signal coming from the atria, delays it slightly, then passes it
into the ventricles, causing them to beat
Usually the whole heart contracts between 60 and 100 times per minute
with beats spaced evenly. Each contraction equals one heartbeat. This
is called normal sinus rhythm.
animation of heart conduction system)
An arrhythmia may occur for one of several reasons:
of beginning in the sinus node, the heartbeat begins in another
part of the heart.
sinus node develops an abnormal rate or rhythm.
signal bypasses the normal regulation of the AV
patient has a heart block.
arrhythmias occur in people who do not have underlying heart disease.
The vast majority of people with arrhythmias have nothing to fear. They
do not need extensive exams or special treatments for their condition.
some people, arrhythmias are associated with heart disease. In these
cases, heart disease,
not the arrhythmia, poses the greatest risk to the patient.
In a very small number of people with serious symptoms, arrhythmias
themselves are dangerous. These arrhythmias require medical treatment
to keep the heartbeat regular. For example, a few people have a very
slow (bradycardia) or fast (tachycardia)
heartbeat. These patients may have symptoms such as chest pain, shortness
of breath, lightheadedness or fainting because the heart is not pumping
enough blood to the body. If left untreated, the heart may stop beating
and these people could die.
times, there is no recognizable cause of an arrhythmia. Heart disease
may cause arrhythmias. Extra conduction pathways (inherited) in an otherwise
healthy heart may cause certain arrhythmias. Other causes include: stress,
caffeine, tobacco, alcohol, diet pills, and cough and cold medicines.
people have felt their heart beat very fast, experienced a fluttering
in their chest, or noticed that their heart skipped a beat. Almost everyone
has also felt dizzy, faint, or out of breath or had chest pains at one
time or another. Symptoms may include:
(increased awareness of the heart beating faster) This is often
the only symptom for most people.
You should not panic if you experience a few flutters or your heart
races occasionally. But if you have questions about your heart rhythm
or symptoms, check with your doctor.
(also called dysrhythmias) may occur at any age. Sometimes a person
may not be aware they have an arrhythmia.
usual ways to evaluate a rhythm abnormality are similar to those used
to evaluate other health problems. The patient's history is very important.
Questions like these might be asked:
you aware of unusual heartbeats?
anything bring on the arrhythmia? What can you do, if anything,
to make it stop?
it's a fast rate, how fast?
you feel weak, lightheaded or dizzy?
you ever fainted?
medicines may make arrhythmias worse. It's important to tell the doctor
about all prescribed and over-the-counter medicines that you take.
the doctor will take a medical history and do a thorough physical exam.
Then one or more tests may be used to check for an arrhythmia and to
decide whether it is caused by heart disease. Sometimes an arrhythmia
can be detected by listening to the heart with a stethoscope. To identify
an arrhythmia, the heart's activity must be recorded on an electrocardiogram
(ECG or EKG).
An arrhythmia may not occur at the time of the exam even though symptoms
are present at other times. In such cases, tests will be done if necessary
to find out whether an arrhythmia is causing the symptoms.
for Detecting Arrhythmias
(ECG or EKG). Records the electrical
activity of the heart. Each time the heart beats, it sends out
an electric-like signal. An ECG machine can record this activity.
To record the ECG, small patches or stickers called electrodes
are placed on different parts of the body. One is put on each
arm and leg and six across the chest.
With various combinations of these electrodes, different tracings
of the heart's electrical activity can be made and permanently
recorded on paper or in a computer. The types of ECGs are:
ECG. The patient lies down for a few
minutes while a record is made. In this type of ECG, disks
are attached to the patient's arms and legs as well as
to the chest. Records about 12 seconds of heart electrical
ECG (stress test). The patient exercises
either on a treadmill machine or bicycle while connected
to the ECG machine. This test tells whether exercise causes
arrhythmias or makes them worse or whether there is evidence
of inadequate blood flow to the heart muscle ("ischemia").
Records electrical activity for duration of exercise (10
to 20 minutes).
ECG (Holter) monitoring. The patient
goes about his or her usual daily activities while wearing
a small, portable recorder that connects to the disks on
the patient's chest. Over time, this test shows changes
in rhythm (or "ischemia") that may not be detected during
a resting or exercise ECG. Can record continuously for 24
to 48 hours.
monitoring. The patient wears the recorder
and disks over a period of a few days to several weeks.
When the patient feels an arrhythmia, he or she telephones
a monitoring station where the record is made. If access
to a telephone is not possible, the patient has the option
of activating the monitor's memory function. Later, when
a telephone is accessible, the patient can transmit the
recorded information from the memory to the monitoring
station. Transtelephonic monitoring can reveal arrhythmias
that occur only once every few days or weeks.
Electrophysiologic Procedure. Sometimes
it's necessary to study the heart's electrical system
with an intracardiac (within the heart) electrophysiologic
procedure. In this, one or more long, thin tubes (catheters)
are placed into the large blood vessels in the legs, arms
or both. Then the tips of the catheters are moved into
the heart. Once in the heart, the catheters can record
electrical signals from the normal electrical system.
This gives much more precise information than an ordinary
ECG. During these studies, the heart can be stimulated
to beat rapidly or irregularly. The heart's response to
this - and the way electricity moves around the heart
during a tachycardia - helps the cardiologist diagnose
the nature of an arrhythmia. Sometimes abnormal tissue
causing an arrhythmia is then destroyed by heating it
with a probe (called radioablation therapy).
Electrophysiologic Procedure. In
some situations, your cardiologist may recommend that
an esophageal electrophysiologic procedure be done. This
is used to diagnose or treat the type of tachycardia you
have. In this procedure, a thin, soft, flexible plastic
tube is inserted into your nostril and positioned in the
esophagus. (The esophagus is the tube that connects the
mouth and stomach.) Since the esophagus is close to the
upper chambers (atria) of the heart, an ECG recording
there gives more precise information than a regular ECG.
An electrical stimulator may be used to make the heart
beat faster to try to restart your arrhythmia. This helps
your doctor make the right diagnosis.
this procedure certain medications may be tested to
find the one that will be most effective. The esophageal
electrophysiologic procedure also may be performed to
temporarily stop certain types of arrhythmias. This
procedure is similar, but less invasive than an intracardiac
procedure. Ablation therapy (directly destroying abnormal
heart conduction tissue) cannot be performed with the
are the different types of an arrhythmias?
are many types of arrhythmias. Arrhythmias are identified by where they
occur in the heart (atria or ventricles) and by what happens to the
heart's rhythm when they occur.
Arrhythmias arising in the atria are called atrial or supraventricular
(above the ventricles) arrhythmias. Ventricular arrhythmias begin in
the ventricles. In general, ventricular arrhythmias caused by heart
disease are the most serious.
in the Atria
Normal cyclic changes in the heart rate during breathing.
Common in children and often found in adults.
The sinus node sends out electrical signals faster
than usual, speeding up the heart rate. A heart rate greater
than 100 beats per minute.
Sometimes the sinus node,
as well as the AV node, doesn't work
properly. Different combinations of supraventricular arrhythmias,
both slow and fast, are produced on an intermittent basis.
This condition almost always indicates disease of multiple
areas of the heart conduction system. Symptoms of sick sinus
syndrome are caused by either too fast or slow heart rate
and include near syncope or syncope (passing out due to not
enough blood reaching the brain), chest pain, shortness of
breath, palpitations and stroke.
Holter monitoring (a device continuously recording heart electrical
activity for 1-2 days) is often needed to diagnose sick sinus
syndrome. A routine EKG often does not show intermittent arrhythmias
common in this syndrome.
Bradycardias causing symptoms usually
require a pacemaker. Tachycardias
are usually treated with medication to slow the heart rate
down. Medications are usually started after pacemaker insertion
because they can make bradycardias worse.
Atrial Contraction (PAC)
Irregular heart rhythms are most often caused by premature
beats or extra beats. These originate in the upper chambers
(premature atrial contraction, PAC). When we feel our heart
"skip a beat," it usually results from this type of arrhythmia.
The heart does not skip a beat. Instead an extra beat comes
sooner than normal. This is followed by a pause that causes
the next beat to be more forceful. The person feels this
beats are common in healthy people of all ages- most people
have them at some time. Caffeine, alcohol, stress and fatigue
may cause PAC's to occur more frequently. Usually no special
treatment is needed and no cause can be found. The premature
beats may disappear, and even if they continue, most people
tolerate them well.
A series of early beats in the atria speed up the
heart rate (the number of times a heart beats per minute).
In paroxysmal tachycardia, repeated periods of very fast heartbeats
begin and end suddenly.
The most common abnormal tachycardia in children (and common
in adults as well) is reentrant supraventricular tachycardia
(SVT). It's also known as paroxysmal atrial tachycardia (PAT)
or paroxysmal supraventricular tachycardia (PSVT). The fast
heart rate involves both the heart's upper and lower chambers.
This isn't a lifethreatening problem for most people. For
many, it doesn't require medical therapy. Treatment is considered
if episodes are prolonged or frequent. There are several subgroups
of SVT, including Wolf-Parkinson-White syndrome (WPW). The
heart rate is generally between 160-200 beats per minute which
can be tolerated by most people for an extended period of
A specific type of SVT this condition is caused by abnormal
pathways between the atria and ventricles, causing the electrical
signal to arrive at the ventricles too soon and to be transmitted
back into the atria. Very fast heart rates may develop as
the electrical signal ricochets between the atria and ventricles.
Sometimes the heart rate can be very high (200-300 beats per
minute). Some medications used to slow regular SVT down can
actually make the heart beat even faster in a particular type
Rapidly fired signals cause the muscles in the atria to contract
quickly, leading to a very fast (250-350 atrial beats per
minute) and regular heartbeat. There is normally a conduction
block at the AV node. That is for any given number of atrial
beats reaching the AV node a certain
number are blocked. Usually one ventricular beat occurs for
every two atrial impulses reaching the AV node. Sometimes
3:1 or even higher block occurs ( that is for every three
atrial impulses reaching the AV node one is conducted through
to the ventricles).
flutter almost always occurs in patients with underlying
heart disease. Atrial flutter is sometimes seen as a transition
rhythm between atrial fibrillation and normal sinus rhythm.
Electrical signals in the atria are fired in a very fast and
uncontrolled manner. Atrial signals are rapid and chaotic
beating upto 400 beats per minute. Instead of a single electrical
signal followed by coordinated atrial contraction there is
quivering of the atrial muscle. Not all signals are conducted
through the AV node. Heart rates may vary from 100 to 180.
Irregular beats (unevenly spaced) heart beats always occur
with atrial fibrillation. (Heart beats are very fast but regular
in PSVT). Atrial fibrillation can occur in a sustained manner
or may occur episodically.
atria do not effectively pump blood. Because most of the
blood filling the ventricles does not require atrial pumping
(blood flows passively into the ventricles from the atria
during the heart's rest cycle) most people still have enough
blood flow to the body's organs. Atrial fibrillation is
usually due to atrial dilatation and associated with four
rheumatic heart disease
high blood pressure
ischemic heart disease (coronary artery disease)
may infrequently occur in young to middle aged healthy
It is important for your doctor to know is you have atrial
fibrillation because of increased risk of stroke. Small emboli
( blood clots) are more likely to form in the atria because
blood does not move as well. When these emboli break loose
they may travel to the brain or other organs.
in the Ventricles
ventricular complexes (PVC) An electrical signal
from the ventricles causes an early heart beat that generally
goes unnoticed. The heart then seems to pause until the next
beat of the ventricle occurs in a regular fashion. Premature
beats are common in healthy people of all ages- most people
have them at some time. Usually no special treatment is needed
and no cause can be found. The premature beats may disappear,
and even if they continue, most people tolerate them well.
Occasionally PVC's may be caused by disease or injury to the
tachycardia (VT) .
The heart beats fast due to electrical signals arising from
the ventricles (rather than from the atria). It's a potentially
serious condition that could threaten a person's life. Heart
rate ranges from 150 to 200 beats per minute. Certain medications
can make this condition worse.
almost always results from serious heart disease such as
coronary artery disease and acute heart attacks; it usually
requires prompt treatment. Ventricular tachycardia, rare
in children, occurs more frequently as people age. Often
specialized tests, including an intracardiac electrophysiologic
procedure (see Special Tests), may be needed to evaluate
the tachycardia and the effect of drug treatment. Some forms
of VT may not need treatment.
Electrical signals in the ventricles are fired in a very fast
and uncontrolled manner, causing the heart to quiver rather
than beat and pump blood. This is the rhythm responsible for
"shocking" unconscious people on television shows.
The ventricle "quivers" with no effective pumping
of blood. The heart has not actually stopped. Because the
heart does not pump blood to the body a person in ventricular
fibrillation loses consciousness immediately.
is almost always seen in patients with severe coronary artery
disease. Much less commonly it may occur in younger people
with normal coronary arteries who have certain inherited
heart conditions and in people who have had the heart muscle
or conduction system injured by infection (myocarditis).
VF may also occur with a very hard blow to the chest, abnormal
concentrations of certain minerals in the body, too low
a body temperature (hypothermia), and when the amount of
certain medications in the body is too high.
cardioversion, using DC current, is always the first
treatment. With an electrical shock, it immediately disrupts
a deadly arrhythmia. To have any chance of recovery cardioversion
must be done quickly. CPR is started
if cardioversion unsuccessful after 3 consecutive attempts.
the complete absence of heart electrical activity. This is
often a terminal arrhythmia usually causing death. That is
other arrhythmias, such as ventricular fibrillation, progress
to asystole if not treated. The heart does not pump or even
block is a condition in which the electrical signal cannot travel normally
down the special pathways to the ventricles. It doesn't mean the blood
flow is blocked; it means that the flow of the electrical signal within
the heart is blocked. For example, the signal from the atria to the
ventricle may be (1) delayed, but each one conducted; (2) delayed with
only some getting through; or (3) completely interrupted. If there is
no conduction, the beat generally originates from the ventricles and
is very slow.
arrhythmias require no treatment . Serious arrhythmias are treated in
several ways depending on what is causing the arrhythmia. Sometimes
the heart disease is treated to control the arrhythmia. Or, the arrhythmia
itself may be treated using one or more of the following treatments.
There are several kinds of drugs used to treat arrhythmias. One
or more drugs may be used. Drugs are carefully chosen because
they can cause side effects. In some cases, they can cause arrhythmias
or make arrhythmias worse. For this reason, the benefits of the
drug are carefully weighed against any risks associated with taking
it. It is important not to change the dose or type of your medication
unless you check with your doctor first.
you are taking drugs for an arrhythmia, one of the following tests
will probably be used to see whether treatment is working: a 24-hour
electrocardiogram (ECG) while you are on drug therapy, an exercise
ECG, or a special technique to see how easily the arrhythmia can
be caused. Blood levels of antiarrhythmic drugs may also be checked.
To quickly restore a heart to its normal rhythm, the doctor may apply
an electrical shock to the chest wall. Called cardioversion, this
treatment is most often used in emergency situations involving potentially
life threatening problems, such as very low blood pressure or decreased
level of consciousness, or in patients who have repeatedly failed
to respond to medication. After cardioversion, drugs are usually prescribed
to prevent the arrhythmia from recurring.
These devices are used to correct serious ventricular arrhythmias
that can lead to sudden death. The defibrillator is surgically placed
inside the patient's chest. There, it monitors the heart's rhythm
and quickly identifies serious arrhythmias. With an electrical shock,
it immediately disrupts a deadly arrhythmia.
An artificial pacemaker can take charge of sending electrical signals
to make the heart beat if the heart's natural pacemaker is not working
properly or its electrical pathway is blocked. It works by sending small,
painless amounts of electricity to the heart to make it beat. During
a simple operation, this small electrical device is placed under the
skin. A lead extends from the device to the right side of the heart,
where it is permanently anchored.
variety of rhythm disorders can be successfully controlled with an artificial
pacemaker. Slow heart rates, such as heart block, are the most common
reason to use a pacemaker. However, new technology now lets doctors
treat some fast heart rates with a pacemaker.
Catheter Ablation and Surgery
Some tachycardias are lifethreatening or significantly interfere
with normal activities. Permanent treatment is often needed for these
procedure, called radiofrequency catheter ablation, is done with several
catheters in the heart. This is called an electrical physiologic study
(EPS testing) and requires a cardiologist with specialized training
as well as special equipment.
therapy involves threading an electrode into the heart through a large
central vein and electrically locating the abnormal conduction tract.
Once the location of the bypass tract is known another catheter is
positioned directly over the area that's causing the tachycardia.
Its tip is heated and that small area of the heart is altered so that
electrical current won't pass through the tissue.
that interrupts the abnormal connection in the heart is another treatment.