The Complex Arrhythmia Program at Memorial Hermann The Woodlands Hospital offers expert care for patients with heart arrhythmias. Here you’ll find:
Premature
(extra) beats
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
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.
Atrial fibrillation
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
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.
Paroxysmal supraventricular
tachycardia (PSVT)
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 (originating in the ventricles)
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
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.
Ventricular fibrillation
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.
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.
Torsades de pointes
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
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.
Arrhythmias in children
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.
Sinus arrhythmia
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.
Sinus tachycardia
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.
Sick sinus syndrome
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.