Table 6

SQTS Diagnostic Criteria

QTc, ms
Jpoint-Tpeak interval <120 ms1
Clinical history
 History of sudden cardiac arrest2
 Documented polymorphic VT or VF2
 Unexplained syncope1
 Atrial fibrillation1
Family history
 First- or second-degree relative with high-probability SQTS2
 First- or second-degree relative with autopsy-negative sudden cardiac death1
 Sudden infant death syndrome1
 Genotype positive2
 Mutation of undetermined significance in a culprit gene1

High-probability SQTS: ≥4 points, intermediate-probability SQTS: 3 points, low-probability SQTS: ≤2 points. Electrocardiogram: must be recorded in the absence of modifiers known to shorten the QT. Jpoint-Tpeak interval must be measured in the precordial lead with the greatest amplitude T-wave. Clinical history: events must occur in the absence of an identifiable etiology, including structural heart disease. Points can only be received for 1 of cardiac arrest, documented polymorphic VT, or unexplained syncope. Family history: points can only be received once in this section.

VF = ventricular fibrillation; VT = ventricular tachycardia; other abbreviations as in Table 1.

  • A minimum of 1 point must be obtained in the electrocardiographic section in order to obtain additional points.