Table 1. Schwartz score.

ECG findings (in the absence of medications or disorders known to affect these features):
• QTc (= QT/√RR, interpret with caution with tachycardia since QTc overcorrects at fast heart rates)
- ≥480 milliseconds: 3 points
- 460 to 479 milliseconds: 2 points
- 450 to 459 milliseconds (in males): 1 point
• QTc at fourth minute of recovery from exercise stress test ≥480 milliseconds: 1 point (27)
• Torsades de pointes* (in the absence of drugs known to prolong QT): 2 points
• T wave alternans: 1 point
• Notched T wave in three leads: 1 point
• Resting heart rate below second percentile for age (restricted to children): 0.5 point
• Clinical findings:
• Syncope* (*points for documented torsades and syncope are mutually exclusive)
- With stress: 2 points
- Without stress: 1 point
• Family history (the same family member cannot be counted in both of these criteria):
• Family members with LQTS: 1 point
• Unexplained SCD in immediate family members <30 years of age: 0.5 point

SCD = sudden cardiac death; low probability ≤1 point; intermediate probability 1.5 to 3 points; high probability ≥3.5 points