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Arrythmia, a fast, irregular heartbeat,
has a variety of causes. One of them has been identified
as Long QT Syndrome. The condition gets its name from
the pattern made on an electrocardiogram (EKG), which
records the heart’s electrical signals. Letters
are assigned to specific points on the waveform, and
when the interval from Q to T is prolonged, it indicates
that there is something wrong with the heart’s
rhythm. For some people, this irregularity causes them
to become dizzy or faint; others go into full cardiac
arrest and suddenly die.
Several genes have been associated with Long QT Syndrome,
although there are non-genetic causes (certain medications
or mineral imbalances) as well. The genes, which have
more than 180 variants, are located on chromosomes 3,
4, 7, 11, and 21. There are different triggers for a
Long QT episode depending which genetic mutation the
person has. People with variants of the LQT3 gene, on
chromosome 3, are prone to abnormal heart rhythms while
they are asleep. When genes are mutated on chromosome
11, arrhythmia typically occurs while the person is
under stress. Genetic changes on chromosome 21 tend
to provoke cardiac electrical abnormalities when a person
is exercising.
Long QT Syndrome is an autosomal dominant condition,
and through mutation scanning ( a blood test) geneticists
can determine if and where there is a gene mutation.
If Long QT Syndrome is known to occur in the family,
a person should strongly consider having the genetic
test. For many, though, genetic testing follows an incident
or two of fainting spells or if there is a sudden, unexplainable
death of an otherwise healthy family member. Additional
clinical tests that a referring physician may order
include an EKG and a stress test.
Many people diagnosed with Long QT Syndrome are prescribed
beta-blockers, which can slow the heart rate. Medicine
is not a cure, however, and is effective only as long
as the patient takes it. When beta -blockers are not
effective, a pacemaker to regulate the heart rate or
an implantable cardioverter defibrillator to shock the
heart back to a regular rhythm can be surgically placed.
Because of its serious implications, it is particularly
important for families with inherited Long QT Syndrome
to discuss test results and their implications with
an experienced genetic counselor along with a cardiologist
with experience in Long QT Syndrome management, and
to perhaps seek counseling support by a mental health
professional.
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Conditions
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