Schwartz et al updated the criteria for the long QT syndrome in 1993. This can help diagnose a patient with the idiopathic long QT syndrome.
Patient preparation: The patient must not be taking a medication known to prolong the QT interval. A person should not be evaluated while suffering from a condition affecting the QT interval.
(1) clinical history of syncope
(2) clinical history of congenital deafness
(3) definite family history of long QT syndrome
(4) unexplained sudden death in an immediate family member not included in #3
(5) long corrected QT interval on ECG
(6) torsade de pointes
(7) T wave alternans
(8) notched T wave in 3 leads
(9) low heart rate for age
clinical history of syncope
family history of long QT syndrome
unexplained sudden death in an immediate family member before age 30
corrected QT interval
< 450 msec
450 msec (in males)
>= 480 msec
torsade de pointes
T wave alternans
leads with notched T waves
heart rate for age
low (< 2nd percentile for age)
• Torsade de pointes and syncope are mutually exclusive.
• The same family member cannot be used to satisfy a family history of LQTS and sudden death.
• The heart rates for age in children are given by Davignon et al (1980).
• The ranges for corrected QT interval given in the original table do not cover a number of situations: (a) female with interval 450 msec; (b) range 451-459; (c) range 471-479. I have set (a) to 0 points; (b) to 1 point; (c) to 2 points in the implementation.
total score =
= MAX((points for syncope), (points for torsade on ECG)) + SUM(points for remaining parameters)
• minimum score: 0
• maximum score: 9.5
Probability of LQTS
2 to 3
• This scheme leaves out scores 1.5 and 3.5. In the implementation I have made 1.5 to 3.5 as intermediate risk.
To read more or access our algorithms and calculators, please log in or register.