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

ECG Images

Shown below is an image of EKG demonstrating QT prolongation

Shown below is an image of EKG demonstrating QT prolongation

Shown below is an image of EKG demonstrating medication induced QT prolongation

Shown below is an image of series of EKG's demonstrating progression of QT prolongation to Torsades de Pointes