This ECG was recorded a few days later from the same patient and is now normal. As mentioned, this type of ECG variability is quite common. Several mutations of the sodium channel gene have been discovered in affected families but a complete understanding of the genetic and electrophysiologic abnormalities responsible for the ECG findings and the ventricular arrhythmias is incomplete. The syndrome is particularly prevalent in southeast Asia where it is a common cause of death in young men. However, families with this disorder have been discovered in all geographic regions and in many ethnic groups.