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Long QT syndrome is a condition that affects the heart’s electrical system and may cause fast, chaotic heartbeats. It can cause fainting, and in some cases cardiac arrest. The heart’s electrical system normally functions by causing the upper chambers (atria) and then the lower chambers (ventricles) to contract. This pattern of normal electrical signals produces a normal ECG (EKG) with Q, R, S, and T waves. In long QT syndrome, the electrical signals are delayed because the electrical system cannot recharge fast enough to carry a signal. This condition increases the risk of a life-threatening abnormal heartbeat (arrhythmia) known as ventricular tachycardia (fast beating of the lower chamber). People with long QT syndrome may have to limit physical activity, avoid certain medications or have an implantable cardioverter defibrillator (ICD) to prevent sudden death.
Long QT Syndrome is a rare disorder of the heart's electrical system that can affect otherwise healthy people. Although the heart's mechanical function is normal, there are defects in ion channels, which are cell structures in the heart muscle. These electrical defects can cause a very fast heart rhythm (arrhythmia) called torsade de pointes. This abnormal rhythm (a form of ventricular tachycardia) is too fast for the heart to beat effectively, so the blood flow to the brain falls dramatically, causing sudden loss of consciousness, or syncope.
Long QT syndrome (LQTS) is a disorder of the heart's electrical activity. It may cause you to develop a sudden, uncontrollable, and dangerous heart rhythm called an arrhythmia (ah-RITH-me-ah) in response to exercise or stress.
Arrhythmias also can develop for no known reason in people who have LQTS. Not everyone who has LQTS develops dangerous heart rhythms. However, if one does occur, it may be fatal.
The term "long QT" refers to an abnormal pattern seen on an EKG (electrocardiogram). An EKG is a test that detects and records the heart's electrical activity. The QT interval, recorded on the EKG, corresponds to the time during which the lower chambers of your heart are triggered to contract and then build the potential to contract again. These chambers are called ventricles (VEN-trih-kuls).
The timing of the heartbeat's electrical activity is complex, and the body carefully controls it. Normally the QT interval of the heartbeat lasts about a third of each heartbeat cycle on the EKG.
However, in people who have LQTS, the QT interval usually lasts longer than normal. This can upset the careful timing of the heartbeat and trigger a dangerous, abnormal rhythm.
This answer from the National Heart, Lung and Blood Institute has been reviewed and/or edited by Dr. William D. Knopf.
Long QT syndrome is an electrical system disorder that puts people at a higher risk of ventricular arrhythmias, or heart-rhythm disturbances. It can be caused by genetics, medications, or a combination of both.
Long QT syndrome is a congenital abnormality of the ability of the heart to conduct electricity properly. Long QT refers to its manifestation on an electrocardiogram. It can cause recurrent bouts of passing out and ultimately sudden death. It is not common.
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