Long QT syndrome (LQTS) is an abnormality in the heart's electrical system that may cause very fast and potentially dangerous heart rhythms or arrhythmias called torsade de pointes. These arrhythmias may cause sudden loss of consciousness and in some cases, sudden cardiac death.
"Long QT" refers to the abnormal pattern on an electrocardiogram (ECG), the test that records the electrical activity of the heart. The "QT" interval is the ECG measure of the period when the lower chambers of your heart are triggered to contract and then prepare to contract again. These chambers are called ventricles.
When Long QT occurs, the interval is longer than usual, triggering a dangerous, abnormal rhythm.
Although the exact frequency of LQTS is unknown, it may be as prevalent as one in 5,000 people and may cause 2,000 to 3,000 sudden deaths in children and young adults each year in the United States.
The most common symptom of long QT syndrome (LQTS) is a sudden loss of consciousness or fainting, called syncope. The condition may also cause seizures and in some instances, cardiac arrest and sudden death.
The severity of the condition varies greatly. Some people never experience syncope and others may have frequent episodes that could possibly lead to cardiac arrest and sudden death.
It is important to note that symptoms usually occur without warning and are caused by a very fast heart rhythm called torsade de pointes. Syncope may occur during or just after physical exertion, emotional excitement or sudden auditory arousal, such as from an alarm clock.
Long QT syndrome (LQTS) is usually diagnosed with an electrocardiogram (ECG), which is a picture of the electrical activity of heartbeats. QT refers to a time interval measured on the ECG. People with this disorder have a longer QT interval than other people.
The ECG isn't a perfect test for the condition. Some people with the disorder will have normal tests or it might be normal on some days and abnormal on other days.
LQTS is usually inherited, which means it may affect multiple family members. Each child, sister, or brother of a person with the disorder has a 50 percent chance of inheriting the genetic mutation that causes the condition.
With the correct diagnosis and therapy, long QT syndrome (LQTS) is a treatable disorder and most deaths are preventable.
Many people with the condition can be treated with medication. A minority of patients need an implantable cardiac defibrillator.
Reviewed by health care specialists at UCSF Medical Center.