The QT interval is the time from the beginning of the QRS complex, representing ventricular depolarization, to the end of the T wave, resulting from ventricular repolarization. The normal QT ...

Long-QT syndrome (LQTS) is characterized by a prolonged QT interval on 12-lead electrocardiograms (ECGs) that can progress to a polymorphic ventricular tachycardia (VT) known as torsades de pointes.

See the ECG Tutorial section on QT interval to learn how this is measured. Multiple medications, electrolyte abnormalities (hypocalcemia, hypomagnesemia and hypokalemia) and certain disease states ...

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