LQTS is suggested if the QTc is longer than these cutoffs. However, as 5% of normal people also fall into this category, some suggest cutoffs of 470 and 480 ms for males and females respectively, corresponding with the 99th centiles of normal values.The major subtypes of inherited LQTS are associated with specific ECG features. LQT1 is typically associated with broad-based T-waves, whereas the T-waves in LQT2 are notched and of lower amplitude, whilst in LQT3 the T-waves are often late onset, being preceded by a long isoelectric segment. Schwartz score
The Schwartz score has been proposed as a method of combining clinical and ECG factors to assess how likely an individual is to have an inherited form of LQTS. The table below lists the criteria used to calculate the score. Other investigations
In cases of diagnostic uncertainty, other investigations may be helpful to unmask a prolonged QT. In addition to prolonging the resting QT interval, LQTS may affect how the QT changes in response to exercise and stimulation by catecholamines such as adrenaline. Provocation tests, in the form of exercise tolerance tests or direct infusion of adrenaline, can be used to detect these abnormal responses. These investigations are most useful for identifying those with concealed congenital Type 1 LQTS 1 (LQT1) who have a normal QT interval at rest. While in healthy persons the QT interval shortens during exercise, in those with concealed LQT1 exercise or adrenaline infusion may lead to paradoxical prolongation of the QT interval, revealing the underlying condition.
Schmitt Gillenwater Kelly syndrome is a rare autosomal dominant congenital disorder consisting of radial hypoplasia, triphalangeal thumbs, hypospadias, and maxillary diastema. References


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