Long QT syndrome (LQTS) is a genetic condition that causes abnormal electrical activity in the heart and may cause fainting or seizure-like episodes. This abnormal activity often occurs during physical activity or in stressful or emotional situations. LQTS is potentially fatal and requires treatment.
LQTS affects approximately 1 in 2,000 people.
Symptoms of LQTS may include fainting, seizures-like episodes, and abnormal, very fast heartbeats. These symptoms may occur during physical activity or exercise, emotional stress, dehydration/electrolyte imbalance, when startled by a loud noise, or while taking certain medications. However, some people with LQTS do not have any symptoms.
The QT interval is one of the heart’s electrical signals that is measured by an ECG; it reflects the time needed by the heart to “recharge” between beats. When the QT interval is too long, the heart may not beat correctly and result in symptoms like dizziness or fainting. People with LQTS typically have an unusually long QT interval.
There are pores in the heart called ion channels that help control electrical activity of the heart. The heart’s electrical system must be carefully regulated because it helps control the heartbeat and mechanical functions of the heart. If these ion channels don’t function properly, LQTS can result.
People with LQTS have hearts that look and sound normal but may have abnormal electrical activity when examined with an electrocardiogram (ECG). In addition to the ECG, a physician may also order genetic testing to help make or confirm a diagnosis of LQTS.
Genetic testing for LQTS is performed to help confirm a suspected diagnosis and identify the specific subtype.A negative genetic test result in an individual with LQTS does not mean the individual does not have LQTS. It simply means we have not yet identified what caused the disease for this individual. Not all individuals with LQTS will have a positive genetic test result.
LQTS can be treated through a combination of medication to control the heartbeat, lifestyle modifications, and in some cases, surgery to insert an implantable cardiac defibrillator (ICD) to monitor and reestablish typical heartbeat. Your cardiologist can help you to make informed medical decisions and provide an opportunity to start risk reduction strategies.
Genetic testing may identify the specific subtype of LQTS, which may help the physician choose the most effective treatment.
If the genetic cause of LQTS is identified in an individual, genetic testing for other family members may be indicated to assess their risk for LQTS and the need for possibly life-saving treatment. Family testing is important because relatives may be at risk regardless of whether or not they are experiencing any symptoms.
Your physician will assist you in identifying and arranging for the appropriate genetic test(s). If you have specific questions or concerns about the testing, your physician may refer you to a genetic counselor to discuss further. Once you are ready to proceed with genetic testing, you will need to submit either a blood or saliva sample.
Jervell and Lange-Nielsen syndrome