NHLBI, Arrhythmia: NHLBI
Article title: NHLBI, Arrhythmia: NHLBI
Conditions: Arrhythmia, heart block, Sinus arrhythmia, Sinus tachycardia, Sick sinus syndrome, premature atrial contractions (PAC) (type of Arrhythmias), Supraventricular tachycardia (SVT) (type of Arrhythmias), paroxysmal tachycardia, Atrial flutter, Atrial fibrillation, Wolff-Parkinson-White syndrome, Premature ventricular complexes (PVC) (type of Arrhythmias), Ventricular tachycardia, Ventricular fibrillation, Ventricular arrhythmias
Facts About Arrhythmias/Rhythm Disorders Table of Contents
is an arrhythmia?
having an arrhythmia mean that a person has heart disease?
common are arrhythmias?
are the symptoms of an arrhythmia?
happens in the heart during an arrhythmia?
is a heart block?
are the different types of arrhythmias?
does the doctor know that I have an arrhythmia?
tests can be done?
for Detecting Arrhythmias
are arrhythmias treated?
can arrhythmias be prevented
research on arrhythmias being done?
can I find publications about heart disease?
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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
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
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.
commonly in middle-age adults. As people get older, they are more likely to
experience an arrhythmia.
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
- 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
- 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
- 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
- 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.
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
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.
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
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
- 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.
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
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.
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
- 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.
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.
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
- 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,
- NHLBI Information Center
P.O. Box 30105
Telephone: (301) 592-8573
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
National Institutes of Health
National Heart, Lung, and Blood
NIH Publication No. 95-2264