| Home | Article Database | Resources | Tools & Just for Fun | Search HY |
Facts About Arrhythmias/Rhythm Disorders
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
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
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.
How common are arrhythmias?
Arrhythmias occur commonly in middle-age adults. As people
get older, they are more likely to experience an arrhythmia.
What are the symptoms of 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
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,
- 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
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
- 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.
What happens in the heart during an arrhythmia?
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
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:
What is 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.
- 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.
What are the different types of an arrhythmias?
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
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.
How does the doctor know that I have arrhythmia?
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.
What tests can be done?
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.
Tests for Detecting Arrhythmias
How are arrhythmias treated?
Many arrhythmias require no treatment whatsoever.
- 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
- 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.
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.
How can arrhythmias be prevented?
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.
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
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 from
- 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
Is research on arrhythmias being done?
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.
Where can I find publications about heart disease?
To obtain publications about heart disease, you may want to
The National Heart, Lung, and Blood Institute also has
publications about heart disease. For more information,
- local American Heart Association chapter.
- local or state health department.
- NHLBI Information Center
P.O. Box 30105
Bethesda, MD 20892-0105
Telephone: (301) 251-1222
Information provided by NIH.