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?
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.
No,
not necessarily. Many arrhythmias occur in people who do not have
underlying heart disease.
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.
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.
|
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.
|
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.
Reference:
from the National Heart, Lung, and Blood Institute
Next
Article