Torsades De Pointes

Long QT Syndrome

Cardiovascular

Written by the doctors and editors at UpToDate
What is long QT syndrome? — Long QT syndrome is a condition that affects the heart's electrical system. It sometimes leads to serious heart rhythm problems that can be life threatening.
There are 2 main types of long QT syndrome:
A type that people are born with – This is caused by an abnormal gene.
A type that happens later in life that people are not born with – Certain medicines can cause long QT syndrome. Mineral imbalances in the body, such as having too little potassium or magnesium, can also cause long QT syndrome.
What are the symptoms of long QT syndrome? — Many people with long QT syndrome have no symptoms. They find out they have it after they have a test called an electrocardiogram done for another reason. An electrocardiogram (also called an "ECG") measures the electrical activity in the heart (figure 1).
When long QT syndrome causes symptoms, they can include:
Heartbeat changes called "palpitations" – These can feel like your heart is beating hard or fast, or skipping beats.
Fainting, or feeling like you are going to faint
Seizures – Seizures are waves of abnormal electrical activity in the brain that can make people pass out or move or behave strangely.
Sudden cardiac arrest – This is when the heart suddenly stops beating. It is a medical emergency that needs to be treated right away.
Is there a test for long QT syndrome? — Yes. An ECG usually shows whether someone has long QT syndrome. But some people will have other tests, too. These can include:
A Holter monitor – This is a heart monitor device that records your heart's electrical activity over hours or days. You wear it around at home while you go about your usual activities (figure 2).
A stress test – During this test, a doctor, nurse, or physician assistant records your ECG while you exercise on a treadmill or bike, or get medicine to make your heart pump faster (figure 3).
Tests to see how your heartbeat changes when you get certain medicines
Blood tests, including tests to check for the abnormal gene that causes long QT syndrome
How is long QT syndrome treated? — Treatment depends mostly on whether you were born with long QT syndrome or developed it later in life.
For people who were born with long QT syndrome, the main treatment includes medicines called beta blockers. These medicines help keep the heart from beating too fast. Some people need other treatments, too. These can include:
Other types of heart medicines
A pacemaker – This is a device that goes under the skin near a person's heart. It sends electrical signals to the heart to control the heartbeat.
An implantable cardioverter-defibrillator (called an "ICD") – This is a device that is put under a person's skin near his or her heart. It can sense abnormal heartbeats and then treat them with an electrical shock.
For people who develop long QT syndrome later in life, treatment can include:
Stopping any medicine that could be causing the long QT syndrome
Fixing the mineral imbalance that is causing the long QT syndrome
A pacemaker
Medicines that control the speed or rhythm of the heartbeat
All people with long QT syndrome who have a sudden cardiac arrest should be treated with defibrillation. This involves using a device to send an electrical shock to the heart. It sometimes works to get a normal heart rhythm started again.
What else should I do? — If you have long QT syndrome, you should:
Follow all of your doctor's instructions about follow-up tests, so that he or she can monitor your condition.
Avoid taking medicines that are likely to cause long QT syndrome. Your doctor can give you a list of these medicines.
Let your family members know. Because long QT syndrome can run in families, they might need to be tested for the condition, too.
Ask your doctor or nurse whether you need to make any lifestyle changes. With some types of long QT syndrome that people are born with, abnormal heart rhythms are triggered by certain things. These include intense exercise, loud or sudden noises, or diving into cold water. If you have this type of long QT syndrome, you will need to avoid these triggers as much as possible.
All topics are updated as new evidence becomes available and our peer review process is complete.
This topic retrieved from UpToDate on: Mar 30, 2020.
Topic 86973 Version 5.0
Release: 28.2.2 - C28.105
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© 2020 UpToDate, Inc. and/or its affiliates. All rights reserved.