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LQTS is a disturbance of the heart's electrical system, causing
an abnormality of the heartbeat. Such an abnormality in the
rhythm of the heart is called arrhythmia. There are other
types of arrhythmias besides LQTS.
Because of the arrhythmia, people with LQTS are vulnerable
to sudden loss of consciousness (called syncope) and even
death. Unfortunately, many times the loss of consciousness
is misdiagnosed and dismissed as simple fainting spells or
seizures. Most often, these events occur during physical exertion
or emotional stress. In some, they occur during sleep. Fortunately,
most of these deaths are preventable if the condition is recognized
and treated.
Your symptoms depend on the type of abnormal heart rhythm
that occurs and how long the abnormal rhythm lasts. The severity
of your symptoms depends on whether your heart spontaneously
snaps out of the abnormal rhythm.
The most common symptom is a fainting episode that may be
triggered by physical exertion, emotional distress, being
startled, or medications. The faint results because the heart's
electrical system spins out of control and the heart muscle
can't pump enough blood to the brain. However, the individual
wakes up because the heart returns to a normal rhythm on its
own, restoring blood flow to the brain.
These symptoms most commonly begin in pre-teen to teenage
years, but may occur from a few days of age to middle age.
Many people with LQTS never have a symptom and lead a normal
life. Others, however, may experience sudden death as the
first symptom because the heart's electrical system never
regains control.
Any young person who has experienced unexplained fainting
should be tested.
The diagnosis is made from an EKG and in-depth medical history.
In some cases, an exercise EKG or event monitor will clarify
the diagnosis.
It is extremely important that all family members be tested
for LQTS once any family member is identified as a a Long
QT Syndrome patient.
Treatment is very effective in the vast majority of patients.
Medications called beta-blockers are effective in about 90%
of patients.
In the remaining cases, an impantable defibrillator/pacemakerpacemaker
is used.
In some cases, both beta-blockers and a defibrillator are
used.
Anyone who experiences loss of consciousness during or immediately
following exercise, emotional distress, or when startled,
particularly in cases where the events reoccur.
Anyone who has a family hstory of unexplained sudden death
in otherwise healthy young persons.
Anyone with a family member already diagnosed with LQTS.
Resting Electrocardiogram (EKG) - This will detect some people
who have Long QT Syndrome. However, sometimes the resting
EKG is not able to diagnose LQTS. In this case, doing EKG's
on other family members will help to diagnose LQTS. Since
this is a genetic condition, a child suspected of having the
Long QT Syndrome would most likely have a parent with the
syndrome, and very likely siblings with the syndrome as well.
Therefore, evaluation of the EKG's of the parents and siblings
of a suspected Long QT patient can also assist in making a
diagnosis.
Exercise (stress) Electrocardiogram (EKG) - This test, which
allows a person to exercise for 10 to 15 minutes without achieving
a heart rate more than 150-160 beats per minute, works best
for screening LQTS. The standard treadmill test, which is
used for detecting cornonary artery disease, is not as good
for detecting LQTS.
LQTS is a disorder of the electrical system of the lower chambers
of the heart (ventricles). The mechanical or pumping function
of the heart is normal. However, the recharging system of
the heart is either slow, inefficient, or taking longer than
normal to recharge. The recharging process allows the heart
muscle to relax, fill with blood and prepare for the next
beat.
The electrical activity of the heart can be recorded as waves
in a test called an electrocardiogram. The different parts
of the waves are labeled with different letters - P, Q, R,
S, and T. The QT interval is a measure of the time it takes
for the electrical system in the ventricles to recharge after
each heartbeat. (See
figure)
Physicians can measure the QT interval and determine if
it is longer than normal. When the QT interval is longer than
normal or the T waves look abnormal, your heart might beat
abnormally. With a long QT interval, your ventricles are more
vulnerable to spin electrically out of control into very fast,
abnormal rhythms.
LQTS may be genetic or acquired. Genetic LQTS occurs when
a change or defect develops in one or more of the genes. For
most people with LQTS, it is likely that the genetic abnormality
has been present in many generations of the family and may
affect several other family members. Often the syndrome has
been undiagnosed, so the frequency with which it appears is
unknown. This means that all relatives need to be evaluated
carefully for LQTS when the inherited form is diagnosed.
It is also possible for a person to be the first of his/her
family members to have the LQTS gene defect. This is called
a spontaneous mutation, and there is a 50:50 chance of passing
on the mutation to their children.
LQTS can also be acquired. There are many external factors
(such as medications, abnormal electrolyte balance, and medical
conditions) that can prolong the QT interval and cause acquired
LQTS. Medications are the most common cause of acquired LQTS.
There are several types of medications (antibiotics, antidepressants,
etc.) that may prolong the QT interval. It is important that
people with inherited LQTS do not take any of these medications
without careful consideration by their physican. If you have
inherited LQTS, always ask your physician or pharmacist to
do a "QT safety check" for all prescribed medications.
For complete medication information, consult the SADS list
of drugs to avoid or the
University of Arizona's QT Drug.org.
For more information, contact:
Sources: The above information was
obtained from the Sudden Arrhythmia Death Syndromes (SADS)
Foundation and from the Long QT syndrome (LQTS) patient education
booklet published by the Mayo Clinic.
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