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(Circulation. 2002;105:784.)
© 2002 American Heart Association, Inc.

The Cardiology Patient Page

The Long-QT Syndrome

Arthur J. Moss, MD; Jennifer L. Robinson, MS

From the Heart Research Follow-up Program of the Cardiology Unit of the Department of Medicine, University of Rochester Medical Center, Rochester, NY.

Correspondence to Arthur J. Moss, MD, Heart Research Follow-up Program, Box 653, University of Rochester Medical Center, Rochester, NY 14642. E-mail heartajm@heart.rochester.edu

The heart is a pump that is stimulated by electrical signals to beat between about 50 to 180 times per minute, depending upon the individual’s level of activity and emotional state. The heart itself is made up of millions of cells that generate repetitive sequences of electrical discharges (referred to in medicine as depolarization) and recharging (repolarization) that produce each heart beat. Electrical activity of the heart cells is produced by the synchronized movement of sodium, potassium, and calcium ions into and out of the cells.

Long-QT Syndrome
Long-QT Syndrome (LQTS) is a disorder of the electrical activity of the heart that can result in blackouts (fainting, also known as syncope) or sudden cardiac death. It occurs infrequently and is caused either by an inherited genetic condition (inherited form of LQTS) or by some prescription medications (acquired form of LQTS). QT refers to the interval on ECG between the beginning of the heart’s electrical discharge through its electrical recovery (see Figure 1). Figure 1 illustrates how the QT interval is measured on the ECG.

View larger version (49K): [in this window] [in a new window]   Schematic diagram of the electrical activity of one heart beat recorded by an ECG. The electrical discharge (depolarization) of the ventricle is represented by the QRS complex, with the T wave reflecting electrical recovery (repolarization). The QT is the time interval from the beginning of the QRS complex to the end of the T wave, and is generally less than 0.44 seconds in normal individuals. In subjects with the long-QT syndrome, the QT is usually longer than . . . [Full Text of this Article]

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