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Long QT Syndrome

Causes Fast, Chaotic Heartbeats

Long QT syndrome (LQTS) is a rare disorder of the heart's electrical rhythm that can occur in otherwise healthy people. It can potentially cause fast, chaotic heartbeats. These rapid heartbeats can lead to fainting. In some cases, your heart's rhythm may be so erratic that it can lead to sudden death.

Usually Affects Children Or Young Adults

Long QT syndrome usually affects children or young adults. Most people experience their first episode before the age of 40. The condition can be hereditary, but can also be caused by any of a number of common medications or by a congenital heart defect.

Long Q-T Interval On Electrocardiogram


When your heart contracts, it sends out an electrical signal. The signal can be recorded on an electrocardiogram (EKG) test and produces a typical waveform. The different parts of this waveform are represented by letters -- P, Q, R, S and T. The Q-T interval represents the time for electrical activation and inactivation of the ventricles, the lower chambers of your heart. Your doctor can measure the time it takes for the Q-T interval to occur in fractions of a second, and can determine if it occurs in a normal or prolonged amount of time.

Heart Muscle Takes Longer To Recharge Between Beats

If this takes longer than normal, it is known as a prolonged Q-T interval. It means that your heart muscle is taking longer than normal to recharge between beats, a process known as repolarization. If this is happening, you have long QT syndrome. The condition is treatable.

Contact Information

Cardiovascular Medicine
Division of the CardioVascular Institute
Beth Israel Deaconess Medical Center
330 Brookline Avenue
Boston, MA 02215