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Long QT Syndrome (LQTS) in Children

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Long QT syndrome (LQTS) is a genetic condition that affects the flow of ions into and out of the cells in the heart. This abnormal flow of ions can prolong the patient’s QT interval, which is measured on an ECG.  The prolonged QT interval affects how electrical impulses travel through the heart.  Electrical activity may be transmitted abnormally through the lower heart chambers (ventricles) leading to potentially life-threatening ventricular arrhythmias. LQTS is usually, but not always, inherited.

Signs and Symptoms

Symptoms of LQTS may include:

  • palpitations
  • syncope (fainting)
  • sudden death
  • seizures or drop spells, especially following sudden startles, such as fire alarms
  • symptoms triggered by stress or physical activity, particularly swimming

In certain patients, there are no symptoms.


Screening for LQTS includes measuring the QT interval on a resting ECG.

An exercise stress test is used to look for changes in the QT interval or abnormal heart rhythm with exercise.

drug (medication) infusion study can help the electrophysiology team determine if patients have certain kinds of cardiac (heart) genetic syndromes or channelopathies.

Genetic Testing and genetic counseling can be valuable tools when evaluating patients and their family members for channelopathies.


Treatment of Long QT syndrome focuses on preventing and treating ventricular arrhythmias.  Your cardiologist may prescribe medications which lessen the effect of catecholamines in our bodies, or which affect the ion channels of the heart cells, or other types of medications used to treat abnormal heart rhythms. Most often, a beta blocker is prescribed.

Implantation of an implantable cardioverter defibrillator (ICD or defibrillator) may be indicated for certain patients, especially those who have had a life-threatening arrhythmia (such as ventricular tachycardia, ventricular fibrillation, or non-vasodepressor syncope while managed on beta blocker).

Depending on the diagnosis, and the severity and frequency of a patient’s episodes, a surgery (sympathetic denervation) to cut the nerve that makes the heart respond to catecholamines may be offered.  This surgery may take place before or after ICD implantation. Even after ICD implantation, patients may be required to continue with their medications and activity restrictions.

Lifestyle Changes:

Some patients with Long QT syndrome may be restricted from competitive sports, and some may require even stricter limitations. Even if there are some restrictions, it will be important to discuss the activities that are safe and appropriate for the patient, and to focus on what CAN be done and how to stay safe when participating in activities.

Patients with Long QT syndrome should avoid medications that prolong the QT interval. A comprehensive and up-to-date list can be found at

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