TABLE 3.

Schwartz criteria to calculate long QT syndrome risk

ECG finding	Score, points
QTc duration* (Bazett formula)
≥480 ms	3
460–479 ms	2
450–459 ms (men only)	1
Torsades de pointes	2
T-wave alternans	1
Notched T wave in 3 leads	1
HR <2nd percentile for age	0.5
Clinical history
Syncope†
With stress/exertion	2
Without stress	1
Congenital deafness	0.5
Family history‡
Family member with definite LQTS	1
Unexplained sudden cardiac death < age 30	0.5

Scoring: ≤1, low probability of LQTS; 2–3, intermediate probability of LQTS; ≥4, high probability of LQTS.

ECG, electrocardiogram; HR, heart rate; LQTS, long QT syndrome.

^*In absence of drugs or conditions that affect QTc.

^†Mutually exclusive.

^‡Cannot be same family member to count both family history categories.