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Table 2 1993–2006 Long QT syndrome (LQTS) diagnostic criteria

From: Congenital long QT syndrome

    POINTS
ELECTROCARDIOGRAPHIC FINDINGS #  
A QTc^ > 480 ms 3
   460 – 470 ms 2
   450 – 459 (male) ms 1
B TORSADE DE POINTES * 2
C T WAVE ALTERNANS 1
D NOTCHED T WAVE IN 3 LEADS 1
E LOW HEART RATE FOR AGE @ 0.5
CLINICAL HISTORY  
A SYNCOPE * WITH STRESS 2
   WITHOUT STRESS 1
B CONGENITAL DEAFNESS 0.5
FAMILY HISTORY $  
A FAMILY MEMBERS WITH DEFINITE LQTS 1
B UNEXPLAINED SUDDEN CARDIAC DEATH BELOW AGE 30 AMONG IMMEDIATE FAMILY MEMBERS 0.5
  1. # In the absence of medications or disorders known to affect these electrocardiographic features
  2. ^ QTc calculated by Bazett's formula where QTc = QT/√RR
  3. * Mutually exclusive
  4. @ Resting heart rate below the 2nd percentile for age
  5. $ The same family member cannot be counted in A and B
  6. SCORE: ≤ 1 point = low probability of LQTS
  7. > 1 to 3 points = intermediate probability of LQTS
  8. ≥ 3.5 points = high probability of LQTS