Which studies are included in the evaluation of suspected long QT syndrome (LQTS)?

Updated: Nov 29, 2017
  • Author: Ali A Sovari, MD, FACP, FACC; Chief Editor: Mikhael F El-Chami, MD  more...
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Diagnostic studies in patients with suspected LQTS include the following:

  • Serum potassium and magnesium levels
  • Thyroid function tests
  • Pharmacologic provocation with epinephrine or isoproterenol in patients with a borderline presentation
  • Electrocardiography of the patient and family members
  • Genetic testing of the patient and family members

An increased corrected QT (QTc) interval in response to standing up (“response to standing” test), which is associated with increased sympathetic tone, can provide more diagnostic information in patients with LQTS. [1] This increase in QTc in response to standing may persist in these patients even after their heart rate returns to normal. [2]

See Workup for more detail.

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