About Arrhythmia
The heart normally beats to a regular rhythm
set by electrical signals sent from an area called the sinus node. A heart
arrhythmia, or irregular heartbeat, occurs when the body sends those electrical
signals too quickly, too slowly or erratically. Arrhythmias can be caused by:
- Alcohol use (especially binge drinking)
- Caffeine
- Congestive heart failure
- Coronary artery disease (especially after
a heart attack or coronary artery bypass surgery)
- Drug abuse
- High blood pressure (hypertension)
- Hypertrophic cardiomyopathy
- Medications and supplements
- Obesity
- Overactive thyroid gland (hyperthyroidism)
- Pericarditis
- Smoking
- Valvular heart disease (especially mitral stenosis and mitral regurgitation)
There are
many types of arrhythmias. Arrhythmias are identified by where they occur in
the heart (in the atria or ventricles) and by what happens to the heart's rhythm
when they occur.
Arrhythmias that begin 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.
Premature
beats are the most common type of heart arrhythmia. They are harmless most of
the time and often don’t cause any symptoms. When symptoms do occur, they
usually feel like a fluttering in the chest or a sensation of a skipped beat.
Most of the time, premature beats need no treatment, especially in otherwise
healthy people.
Premature
beats that occur in the atria are called premature atrial contractions, or
PACs. Premature beats that occur in the ventricles are called premature
ventricular contractions, or PVCs.
In most
cases, premature beats occur naturally, not due to any heart disease. But
certain heart diseases can cause premature beats. They also can happen because
of stress, too much exercise, or too much caffeine or nicotine.
Supraventricular
arrhythmias are tachycardias (fast heart rates) that start in the atria or the
atrioventricular node (cells located between the atria and the ventricles).
Types of supraventricular arrhythmias include atrial fibrillation (AF), atrial
flutter, paroxysmal supraventricular tachycardia (PSVT), and
Wolff-Parkinson-White (WPW) syndrome.
AF
is the most common type of serious arrhythmia. AF is a very fast and irregular rhythm
originating in the atria. AF occurs when the heart’s electrical signal begins
in a different part of the atrium other than where it is supposed to begin, the
sinoatrial (SA) node, which is known as the pacemaker of the heart.
When
this happens, the electrical signal does not travel through the normal pathways
in the atria, but instead may spread throughout the atria in a fast and
disorganized manner. This causes the walls of the atria to quiver very fast
(fibrillate) instead of beating normally. As a result, the atria are not able
to adequately fill with blood or pump blood in sufficient amounts.
The
two most serious complications of chronic (long-term) AF are stroke and heart
failure. Stroke can happen when a blood clot travels to an artery in the brain,
blocking off blood flow. In AF, blood clots can form in the atria because some
of the blood “pools” in the fibrillating atria instead of flowing into the
ventricles. If a piece of a blood clot in the left atrium breaks off, it can
travel to the brain, causing a stroke. People with AF are often treated with
blood-thinning medicines to reduce the chances of developing blood clots.
Heart
failure occurs when the heart cannot pump enough blood to meet the needs of the
body. AF can cause heart failure when the ventricles beat too fast and do not
have enough time to fill with blood to pump out to the body. Heart failure
causes tiredness, leg swelling and shortness of breath.
AF
and other supraventricular (originating above the ventricles) arrhythmias can
occur for no apparent reason. Most of the time, however, supraventricular
arrhythmias are caused by an underlying condition that interferes with the
heart’s ability to conduct electrical impulses. These conditions include high
blood pressure (hypertension), coronary artery disease, heart failure or
rheumatic heart disease.
Other
conditions also can lead to AF, including overactive thyroid gland (too much
thyroid hormone produced) and heavy alcohol use. AF also becomes more common as
people get older.
Atrial
flutter is similar to atrial fibrillation, but instead of the electrical
signals spreading through the atria in a fast and irregular rhythm, they travel
in a fast and regular rhythm. Atrial flutter is much less common than atrial
fibrillation, but has similar symptoms and complications. The atria contract at 300 beats per minute. The lower chambers
(the ventricles) contract at multiples of this (150, 100, or 75 beats per
minute). The usual rate is 150 beats per minute.
PSVT
is a very fast heart rate that begins and ends suddenly. PSVT occurs due to
problems with the electrical connection between the atria and the ventricles.
In PSVT, electrical signals that begin in the atria and travel to the
ventricles can reenter the atria, causing extra heartbeats. This type of
arrhythmia is not usually dangerous and tends to occur in younger people, often
during vigorous exercise.
A
special type of PSVT is Wolff-Parkinson-White
syndrome. WPW syndrome is a condition in which the heart’s electrical
signals travel along an extra pathway from the atria to the ventricles. This
extra pathway disrupts the timing of the heart’s electrical signals and can
cause the ventricles to beat very fast. This type of arrhythmia can be life
threatening.
Ventricular
arrhythmias start in the electrical pathways of the ventricles. They can be
very dangerous and usually require immediate medical attention. Ventricular
arrhythmias include ventricular tachycardia and ventricular fibrillation
(v-fib). Coronary artery disease, heart attack, weakened heart muscle and other
problems can cause ventricular arrhythmias.
Ventricular
tachycardia is a fast, regular beating of the ventricles that may last for only
a few seconds or for much longer. A few beats of ventricular tachycardia often
don’t cause problems, but ventricular tachycardia episodes that last for more
than a few seconds can be dangerous. Ventricular tachycardia can turn into
other, more dangerous arrhythmias, such as v-fib.
V-fib
occurs when disorganized electrical signals make the ventricles quiver instead
of pump normally. Without the ventricles pumping blood out to the body, a
person may lose consciousness within seconds and may die within minutes if not
treated. To prevent death, v-fib requires immediate treatment with
defibrillation, which is an electric shock to the heart. V-fib may happen during
or after a heart attack, or in a heart that is already weak because of another
condition. Health experts think that most of the sudden cardiac deaths that
occur every year (about 335,000) are due to v-fib.
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.
Torsades
de Pointes (torsades) is a specific form of v-fib with a unique pattern on an
EKG (electrocardiogram). Certain medicines and imbalanced amounts of potassium,
calcium, or magnesium in the bloodstream can cause this condition. People with
a particular finding on an EKG test, called prolonged QT interval, are at
increased risk of developing torsades. People with prolonged QT interval need
to be careful about taking certain antibiotics, heart medicines and
over-the-counter medicines.
Bradyarrhythmias
are arrhythmias in which the heart rate is slower than normal. If the heart
rate is too slow, not enough blood reaches the brain, and the person can lose
consciousness. In adults, a heart rate slower than 60 beats per minute is a
bradyarrhythmia. Some people normally have slow heart rates, especially people
who are very physically fit. For them, a heartbeat slower than 60 beats per
minute is not dangerous and does not cause symptoms. However, in other people,
bradyarrhythmia can be due to a serious health condition.
Bradyarrhythmias
can be caused by heart attack, conditions that harm or change the heart’s
electrical system (such as underactive thyroid gland or aging), an imbalance of
chemicals or other substances (such as potassium) in the blood or even some
medicines (such as beta blockers).
Bradyarrhythmias
also can occur due to a condition known as ‘severe bundle branch block.’ Bundle
branch block is a condition in which the electrical signal traveling along
either or both of the electrical pathways between the ventricles, called bundle
branches, is delayed or blocked. When this happens, the ventricles do not
contract at exactly the same time, as they should, and the heart has to work
harder to pump blood to the body. The cause of bundle branch block is often an
existing heart condition.
Normally, a
child’s heart beats between 70 and 100 times a minute. A newborn’s heart beats
about 140 times a minute. A baby or child’s heart can beat faster or slower
than normal for many reasons.
Like adults,
when children are active their hearts beat faster and slower when they are
asleep. Their heart rates can speed up and slow down as they breathe in and
out. All of these changes are normal.
Some children
are born with heart defects that cause arrhythmias. In other children,
arrhythmias can develop later in childhood. Doctors do the same kinds of tests
in children as adults to diagnose arrhythmias.
Treatments
for children with arrhythmias include medicines, electric shock
(defibrillation), surgically implanted devices that control the heartbeat, and
other procedures that fix electrical signals in the heart.
This
is the name for changes in the heart rate that occur during breathing. Sinus
arrhythmia is common in children and often found in adults. This is normal.
The
sinus node sends out electrical signals faster than usual, speeding up the
heart rate. Causes include exercise, fever, excitement, certain medications,
dehydration and an overly active thyroid gland.
The
sinus node does not fire signals properly, so the heart rate slows down.
Sometimes the rate changes back and forth between a slow (bradycardia) and fast
(tachycardia) rate.
Portions of this Information
were provided by the National Heart Lung Blood Institute.