Long QT Syndrome

It is not known exactly how many people have LQTS, but the inherited type is thought to be a common cause of sudden, unexplained death in children and young adults.

The QT Interval

	A waveform on an ECG represents the electrical activity of each heart beat.

The letters, P, Q, R, S, and T represent different parts of each waveform.

The space between the beginning of the Q wave and the end of the T wave (called the QT Interval) is a critical juncture. It represents the time it takes for the heart's electrical system to recharge after each beat (a process called "repolarization") before generating the next signal to activate the ventricles, the major pumping chambers of the heart.

In Long QT Syndrome, the interval between Q and T is longer than normal. People with this syndrome are susceptible to an abnormally rapid heart rhythm (arrhythmia) called "torsade de pointes." When this occurs, the heart muscle cannot contract effectively, and the normal volume of blood is reduced to the body and - most important - to the brain. If the brain is starved of oxygen, the indivdiual faints within seconds. If the heart cannot regain its normal rhythm, it may go into spasms that lead to a deadly arrhythmia called ventricular fibrillation. Without immediate emergency treatment, death follows within minutes.

Fainting is the primary symptom - and may be the only warning sign - of LQTS. Once a person has been diagnosed with the LQTS, all family members should be tested, including the parents, siblings and children of the affected individual.

LQTS is caused by a dysfunction of cells in the heart called ion channels. Ions are "charged" particles found in substances such as sodium and potassium. It is the flow of ions in and out of the cells that produce the heart's electrical activity.

Some medications may cause acquired LQTS. There are at least 50 or more FDA approved medications that are known to prolong the Q-T interval. This generally is not a problem and does not lead to torsades de pointes or other heart rhythm disorders for most people. These medications should be prescribed carefully, however, for people with some types of health problems. They must be avoided altogether by people who already have been diagnosed with LQTS. (Some of these medications may require monitoring in the hospital when they are started.) If you are taking any medications that cause dizziness, fainting, confusion or irregular heart rhythms, notify your doctor immediately.

Drugs that prolong the QT interval and/or induce Torsades De Pointes

The following list of drugs is derived from information found in the labeling of FDA-approved drugs, or in the medical literature. There may be other drugs and/or substances that also cause these heart rhythm problems that are not listed here.