Long QT syndrome (LQTS) is an episode arrhythmia usually first presenting in childhood. The average age of first syncopal episode is 14 years with a one year mortality of 20% after first presentation.
A high degree of suspicion is required if the QTc or corrected QT interval is > .44 seconds. When evaluating for long QTc it is important that the calculation from the beginning of the QRS wave to the end of the T wave be performed manually and not taken from the autocalculation supplied by the ECG machine.
The LQTS syncopal episode can be precipitated by emotional and psychological stress (e.g. fright, anger, pain), during physical exercise, and after sudden startling. The classic scenario is a child who dives into a cold lake or pond with onset of arrhythmia, syncope, and risk of drowning.
Although most cases of LQTS occur as an isolated condition, Jervell and Lange-Nielsen syndrome is a rare autosomal recessive congenital syndrome marked by sensory deafness and LQTS. Any child with deafness and syncopal episodes must be worked up for presence of this condition.