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.
- 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 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
can still lead a long and healthy life.
