Long QT Syndrome
What is long QT syndrome?
Long QT syndrome (LQTS) is a disease that can cause a dangerous rapid heart rate and
irregular rhythm involving the bottom pumping chambers of the heart (ventricles).
The heart has both muscular and electrical components. Electricity flowing through
the heart muscle triggers the muscle to squeeze (contract) or beat. Heart muscle cells
use highly coordinated ion channels to keep the flow of electricity moving to generate
normal heartbeats. Ion channels are what the electrolytes potassium, sodium, and calcium
flow through within the heart's cells. In LQTS, a problem in the ion channels leads
to an upset in the flow of electricity that causes a prolonged "repolarizing" of the
heart cells. This can create a set-up for a very rapid and dangerous heart rhythm
(arrhythmia). This can cause fainting or sudden death. The arrhythmias are called
ventricular tachycardia or ventricular fibrillation.
The name, long QT, stems from a reading on the electrocardiogram (ECG) machine. Healthcare
providers use the ECG to evaluate your heartbeat and rhythm. The ECG machine records
and measures each of your heartbeats as 5 “waves.” Each wave has a different letter
designation: P, Q, R, S, and T. The relationship between the Q and T waves is important
and is known as the QT interval. During this interval, the ventricles (lower chambers)
are "repolarizing" or preparing for the next wave of electricity that will elicit
a heartbeat. When the interval lasts longer than it normally should, it disrupts the
timing of your heartbeat and can cause dangerous arrhythmias, or irregular heart rates.
What causes long QT syndrome?
Often, LQTS is passed down through families (genetic). Only one parent needs the genetic
problem for it to be passed on to the child. If one of your family members is diagnosed
with LQTS, experts advise that you and your other family members — parents, siblings,
children — get tested as well. In rare instances, certain diseases or medicines can
cause acquired LQTS. These diseases and/or medicines may affect the ion channels in
the heart or cause electrolyte problems such as low potassium and calcium. More than
50 medicines list LQTS as a risk. Ask your healthcare provider about the risks of
all medicines you're taking.
Who is at risk for long QT syndrome?
If you have a family history of LQTS, you are at risk of developing it. Specialists
believe that if you are susceptible to long QT syndrome, you are more likely to be
affected by medicines that increase your risk for the condition. Medicines such as
antibiotics, antidepressants, antihistamines, diuretics, and heart medicines may increase
your risk for LQTS.
What are the symptoms of long QT syndrome?
Some people with LQTS have no symptoms. The condition is detected on an ECG or heart
monitor done for other reasons. If ventricular arrhythmias do occur as a result of
LQTS, some symptoms include:
Chest fluttering (palpitations)
Shortness of breath or chest pain
Lightheadedness that comes and goes
Near fainting or fainting
How is long QT syndrome diagnosed?
An ECG is the main way to detect LQTS. If your healthcare provider notes that the
interval between the Q and T waves of your heartbeat is longer than it should be,
you may have LQTS. The QT interval can vary from one visit to the next and can change
with activity. You may be given a Holter monitor. This is a portable, wearable ECG
recording device. You can wear the Holter monitor over several days to get readings
during different activities. Another option is having an ECG during exercise (exercise
stress testing). QT shortening is a normal response to exercise. Genetic testing is
also available for inherited LQTS. It may help identify genetic defects associated
with LQTS. It may also be used to screen first-degree relatives for the condition.
How is long QT syndrome treated?
For acquired LQTS, correcting any electrolyte problems or changing medicines may be
all that is needed. There is no cure for inherited LQTS, but treatment helps prevent
symptoms and lowers the risk for fainting or cardiac arrest. Your doctor may prescribe
medicines called beta blockers to reduce arrhythmias. If you continue to have arrhythmias
that keep coming back, or have had sudden cardiac arrest, you may need an implantable
cardiac defibrillator (ICD). This device is implanted underneath the skin in the front
of the chest wall. A wire connects the device to the heart. The ICD monitors your
heart rhythm. If needed, it can deliver therapy such as ATP (anti tachycardia pacing)
or 1 or more brief electrical shocks to the heart to reset the rhythm.
Surgery is another option for some people with inherited LQTS. It involves removing
certain nerves in your chest that influence the heart rhythm.
What can I do to prevent long QT syndrome?
You can't prevent inherited LQTS but you can reduce your risk for things that can
trigger arrhythmias and sudden death:
See your healthcare provider regularly.
Take your medicines as prescribed. Don't take medicines that prolong the QT.
Follow limits on certain activities such as strenuous exercise and driving.
Stay away from high-stress situations that may trigger LQTS.
Ask your healthcare provider if you need a potassium supplement.
Wear a medical alert bracelet.
When should I call my healthcare provider?
Seek medical attention right away if you:
Also see your healthcare provider for evaluation if you have a family history of unexplained
sudden death at a young age or have a relative with known LQTS.
Key points about long QT syndrome
Long QT syndrome is a rare heart disorder that upsets the electrical activity of your
This electrical disruption can cause an abnormal heartbeat and even sudden death.
Family history of long QT syndrome is the main risk factor for developing the condition.
Medicine or an implantable cardioverter defibrillator (ICD) can help manage the condition.
Long QT syndrome is potentially fatal and requires medical help.
Tips to help you get the most from a visit to your healthcare provider:
Know the reason for your visit and what you want to happen.
Before your visit, write down questions you want answered.
Bring someone with you to help you ask questions and remember what your provider tells
At the visit, write down the name of a new diagnosis, and any new medicines, treatments,
or tests. Also write down any new instructions your provider gives you.
Know why a new medicine or treatment is prescribed, and how it will help you. Also
know what the side effects are.
Ask if your condition can be treated in other ways.
Know why a test or procedure is recommended and what the results could mean.
Know what to expect if you do not take the medicine or have the test or procedure.
If you have a follow-up appointment, write down the date, time, and purpose for that
Know how you can contact your provider if you have questions.