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Congenital long QT syndrome: Diagnosis

Peter J Schwartz, MD
Michael J Ackerman, MD, PhD
Section Editors
John K Triedman, MD
Samuel Asirvatham, MD
Deputy Editor
Brian C Downey, MD, FACC


Long QT syndrome (LQTS) is a disorder of ventricular myocardial repolarization characterized by a prolonged QT interval on the electrocardiogram (ECG) (waveform 1) that can lead to symptomatic ventricular arrhythmias and an increased risk of sudden cardiac death [1]. The primary symptoms in patients with LQTS include syncope, seizures, and cardiac arrest. This syndrome is associated with an increased risk of a characteristic life-threatening cardiac arrhythmia known as torsades de pointes or "twisting of the points" (waveform 2) [2].

LQTS may be congenital or acquired [1,3-7]. Mutations in at least 17 genes have been identified thus far in patients with congenital LQTS; the distinct genetic subtypes are designated LQT1 through LQT17 (table 1) [7]. Acquired LQTS usually results from undesired QT prolongation and potential for QT-triggered arrhythmias by either QT-prolonging disease states, QT-prolonging medications (www.crediblemeds.org), or QT-prolonging electrolyte disturbances (table 2). Acquired LQTS is discussed in detail separately. (See "Acquired long QT syndrome" and "Genetics of congenital and acquired long QT syndrome".)

The ECG features and diagnostic approach to persons with suspected congenital LQTS will be reviewed here [1]. The epidemiology, clinical features, and management of congenital LQTS in children and adults and the clinical features of acquired LQTS are discussed separately. (See "Clinical features of congenital long QT syndrome" and "Prognosis and management of congenital long QT syndrome" and "Acquired long QT syndrome".)


Our approach — Our approach to evaluating the patient with suspected congenital LQTS involves multiple steps [1]:

For all patients, the initial evaluation of suspected congenital LQTS should include obtaining a comprehensive personal and family history, performance of a physical examination, and review of an ECG. The ECG is examined to determine both the length of repolarization (the QTc) and the look of repolarization (T wave morphology).

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Literature review current through: Sep 2017. | This topic last updated: Sep 25, 2017.
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