Arrhythmias
What is an arrhythmia?
An arrhythmia is a change in the
regular beat of the heart or an abnormal heart
rhythm. The heart may seem to skip a beat or
beat irregularly or very fast or very slowly.
The
heart has it's own natural or built in pacemaker
called the sinoatrial node (also called the SA
node or sinus node). In a normal person the SA
node sends out impulses to the right and left
upper chambers (atria) of the heart telling them
it's time to beat. The signal then travels
through the AV node, then into the ventricles
(bottom chambers) via the "His bundle" telling
them to beat. This causes the atria to beat
first and a split second later, the ventricles
beat. This is the most efficient and effective
way for your heart to pump blood to the body. In
a normal person, the AV node is the only way for
heartbeat signals to travel between the top and
bottom chambers of the heart.
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 bottom.
Normally each heartbeat starts in the right
atrium. Here, a special group of cells called
the sinus node, or natural pacemaker, sends an
eletrical signal. The signal spreads throughout
the atria to the area 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.
Causes
Many times, there is no
recognizable cause of an arrhythmia. Heart
disease may cause arrhythmias, but having an
arrhythmia does not mean that you have heart
disease. 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.
-
Use of
caffeine, tobacco, alcohol, diet pills, and
cough and cold medicines
-
Stress
How common and serious are
arrhythmias?
Arrhythmias occur commonly in
middle-age adults. As people get older, they are
more likely to experience an arrhythmia.
The majority of people with
arrhythmias do not need extensive exams or
special treatments for their condition. For
some, arrhythmias are associated with heart
disease, in which case, heart disease, not the
arrhythmias, poses the greatest threat 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. Some
people have a very slow heartbeat, causing them
to feel lightheaded or faint. If left untreated,
the heart may stop beating and these people
could die. For most people, however, these
symptoms are completely harmless.
Symptoms
What is 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 ventricles may be delayed, but each
one conducted:
-
delayed
with only some getting through
-
completely
interrupted
-
if there is
no conduction, the beat generally originates
from the ventricles and is very slow
How are arrhythmias detected?
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 the 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.
How are arrhythmias treated?
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 arrhythmia itself may be treated using
one or more of the following treatments:
There are several kinds of drugs
used to treat arrhythmias and one or more may be
used in combination. Drugs are carefully chosen
because 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.
To quickly restore a heart to
its normal rhythm, the doctor may apply an
electrical shock to the chest wall. This
treatment is called cardioversion and is most
often used in emergency situations. After
cardioversion, drugs are usually used 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 life
threatening arrhythmia.
This device 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. This electrical device is placed under
the skin in a minor operation and a lead is
extended from the device to the right side of
the heart, where it is permanently attached.
When an arrhythmia cannot be
controlled by other treatments, doctors may
decide to 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.
Types of Arrythmias
There are many types of
arrhythmias. Arrhythmias are identified by the
location 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.
Bradycardia
This is characterized by the heart beating
too slow. There may be a problem in your SA
node, AV node or His bundle that doesn't allow
the heart beat to travel through your heart in a
normal fashion. Tachycardia This condition is
characterized by the heart beating at an
abnormally rapid rate and interfering with the
pumping of oxygenated blood throughout the body.
Supraventricular tachycardia
When this occurs, there are abnormal fast
rhythms from the top chambers of the heart.
There are many causes including heart disease,
aging, metabolic imbalances and other medical
problems. Some people are born with the problem
even though it may not be evident until later in
life.
Ventricular tachycardia
This is abnormal fast rhythm from the bottom
chambers of the heart and is a serious and
potentially life threatening heart rhythm
problem. The heart is beating too fast to
effectively pump blood to the body.
Ventricular fibrillation
This is a rhythm problem during which the
heart goes so fast that is essentially not
pumping any blood. Defibrillation must be
performed within seconds to save the patient's
life. Long-term treatment includes medications
or implanted defibrillators.
With proper attention and
treatment, persons who have suffered from
arrhythmia's can still lead a long and healthy
life.
