Arrhythmias/Rhythm
Disorders
Source:
National Heart, Lung, and Blood Institute
Table
of Contents
What is an arrhythmia?
Does having an arrhythmia mean that a person has heart disease?
What causes arrhythmias?
Are arrhythmias serious?
How common are arrhythmias?
What are the symptoms of an arrhythmia?
Arrhythmia Types
What happens in the heart during an arrhythmia?
What is a heart block?
What are the different types of arrhythmias?
How does the doctor know that I have an arrhythmia?
What tests can be done?
Tests for Detecting Arrhythmias
How are arrhythmias treated?
How can arrhythmias be prevented
Is research on arrhythmias being done?
Where can I find publications about heart disease?
What is an arrhythmia?
An arrhythmia
is a change in the regular beat of the heart. The heart may seem to skip a beat
or beat irregularly or very fast or very slowly.
Does having
an arrhythmia mean that a person has heart disease?
No, not necessarily.
Many arrhythmias occur in people who do not have underlying heart disease.
What causes
arrhythmias?
Many times,
there is no recognizable cause of an arrhythmia. Heart disease may cause arrhythmias.
Other causes include: stress, caffeine, tobacco, alcohol, diet pills, and cough
and cold medicines.
Are arrhythmias
serious?
The vast majority
of people with arrhythmias have nothing to fear. They do not need extensive
exams or special treatments for their condition.
In 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 heartbeat (bradycardia), causing
them to feel lightheaded or faint. If left untreated, the heart may stop beating
and these people could die.
Arrhythmias occur
commonly in middle-age adults. As people get older, they are more likely to
experience an arrhythmia.
Most 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. One of the
most common arrhythmias is sinus arrhythmia, the change in heart rate that can
occur normally when we take a breath. These experiences may cause anxiety, but
for the majority of people, they are completely harmless.
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.
Originating
in the Atria
- Sinus
arrhythmia. Cyclic changes in the heart rate during breathing.
Common in children and often found in adults.
- Sinus
tachycardia. The sinus node sends out electrical signals
faster than usual, speeding up the heart rate.
- Sick
sinus syndrome. The sinus node does not fire its signals
properly, so that the heart rate slows down. Sometimes the rate
changes back and forth between a slow (bradycardia) and fast (tachycardia)
rate.
- Premature
supraventricular contractions or premature atrial contractions (PAC).
A beat occurs early in the atria, causing the heart to beat before
the next regular heartbeat.
- Supraventricular
tachycardia (SVT), paroxysmal atrial tachycardia (PAT).
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.
- Atrial
flutter. Rapidly fired signals cause the muscles in the
atria to contract quickly, leading to a very fast, steady heartbeat.
- Atrial
fibrillation. Electrical signals in the atria are fired
in a very fast and uncontrolled manner. Electrical signals arrive
in the ventricles in a completely irregular fashion, so the heart
beat is completely irregular.
- Wolff-Parkinson-White
syndrome. Abnormal pathways between the atria and ventricles
cause 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.
Originating
in the Ventricles
- Premature
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.
- Ventricular
tachycardia. The heart beats fast due to electrical signals
arising from the ventricles (rather than from the atria).
- Ventricular
fibrillation. 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.
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Describing how the
heart beats normally helps to explain what happens during an arrhythmia.
The heart is
a muscular pump divided into four chambers--two atria located on the top and
two ventricles located on the bottom.
Normally each
heartbeat starts in the right atrium. Here, a specialized group of cells called
the sinus node, or natural pacemaker, sends an electrical signal. The signal
spreads throughout the atria to the area between the atria called the atrioventricular
(AV) node.
The AV node
connects to a group of special pathways that conduct the signal to the ventricles
below. As the signal travels through the heart, the heart contracts. First
the atria contract, pumping blood into the ventricles. A fraction of a second
later, the ventricles contract, sending blood throughout the body.
Usually the
whole heart contracts between 60 and 100 times per minute. Each contraction
equals one heartbeat.
An arrhythmia
may occur for one of several reasons:
- Instead of
beginning in the sinus node, the heartbeat begins in another part of the
heart.
- The sinus
node develops an abnormal rate or rhythm.
- A patient
has a heart block.
Heart block is a
condition in which the electrical signal cannot travel normally down the special
pathways to the ventricles. 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.
There 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.
Sometimes an arrhythmia
can be detected by listening to the heart with a stethoscope. However, the electrocardiogram
is the most precise method for diagnosing the arrhythmia.
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.
First 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.
- Electrocardiogram
(ECG or EKG). A record of the electrical activity of the
heart. Disks are placed on the chest and connected by wires to a
recording machine. The heart's electrical signals cause a pen to
draw lines across a strip of graph paper in the ECG machine. The
doctor studies the shapes of these lines to check for any changes
in the normal rhythm. The types of ECGs are:
- Resting
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.
- Exercise
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").
- 24-hour
ECG (Holter) monitoring. The patient goes about his or her
usual daily activities while wearing a small, portable tape
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.
- Transtelephonic
monitoring. The patient wears the tape 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
study (EPS). A test for arrhythmias that involves cardiac
catheterization. Very thin, flexible tubes (catheters) are placed
in a vein of an arm or leg and advanced to the right atrium and
ventricle. This procedure allows doctors to find the site and type
of arrhythmia and how it responds to treatment.
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Many arrhythmias
require no treatment whatsoever.
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 arrhthmia
itself may be treated using one or more of the following treatments.
- Drugs
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.
If 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.
- Cardioversion
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. After cardioversion, drugs are
usually prescribed to prevent the arrhythmia from recurring.
- Automatic
implantable defibrillators
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.
- Artificial
pacemaker
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. During a simple operation, this 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.
- Surgery
When an arrhythmia cannot be controlled by other treatments, doctors may
perform surgery. After locating the heart tissue that is causing the arrhythmia,
the tissue is altered or removed so that it will not produce the arrhythmia.
If heart disease
is not causing the arrhythmia, the doctor may suggest that you avoid what is
causing it. For example, if caffeine or alcohol is the cause, the doctor may
ask you not to drink coffee, tea, colas, or alcoholic beverages.
The National Heart,
Lung, and Blood Institute (NHLBI) supports basic research on normal and abnormal
electrical activity in the heart to understand how arrhythmias develop. Clinical
studies with patients aim to improve the diagnosis and management of different
arrhythmias. These studies will someday lead to better diagnostic and treatment
strategies.
To obtain publications
about heart disease, you may want to contact your:
- local American
Heart Association chapter.
- local or state
health department.
The National Heart,
Lung, and Blood Institute also has publications about heart disease. For more
information, contact:
- NHLBI Information
Center
P.O. Box 30105
Bethesda, MD 20892-0105
Telephone: (301) 251-1222
U.S. DEPARTMENT
OF HEALTH AND HUMAN SERVICES
Public Health Service
National Institutes of Health
National Heart, Lung, and Blood Institute
NIH Publication No. 95-2264
Reprinted September 1995
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