Long QT Syndrome electrocardiogram

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2]

Electrocardiogram

The diagnosis of LQTS is not easy since 2.5% of the healthy population have prolonged QT interval, and 10% of LQTS patients have a normal QT interval. A commonly used criterion to diagnose LQTS is the LQTS "diagnostic score". Its based on several criteria giving points to each. With 4 or more points the probability is high for LQTS, and with 1 or less point the probability is low. Two or 3 points indicates intermediate probability.

• QTc (Defined as QT interval / square root of RR interval)
  • >= 480 msec - 3 points
  • 460-470 msec - 2 points
  • 450 msec and male gender - 1 point

• Torsades de Pointes ventricular tachycardia - 2 points
• T wave alternans - 1 point
• Notched T wave in at least 3 leads - 1 point
• Low heart rate for age (children) - 0.5 points
• Syncope (one cannot receive points both for syncope and Torsades de pointes)
• With stress - 2 points
• Without stress - 1 point

• Congenital deafness - 0.5 points
• Family history (the same family member cannot be counted for LQTS and sudden death)
• Other family members with definite LQTS - 1 point
• Sudden death in immediate family (members before the age 30) - 0.5 points