The T wave is when the heart rests. The QT interval is the length of the time it takes for the entire heartbeat. On the right is a normal heartbeat and the heartbeat of someone with Long QT Syndrome. People with Long QT are susceptible to an arrhythmia that can cause an irregular heartbeat, resulting in fainting or death. No one knows how many people die from Long QT Syndrome, mainly because it doesn't show up on an autopsy.
Cardiologists offer different estimates, ranging anywhere from five to a hundred deaths a year.
Most of the adults are children and young adults and might account for 30 or 40 per cent of sudden deaths in children. The condition runs in families. Aside from family history, there's another warning sign parent can look out for, and that's fainting. Dr. Bob Hamilton, who specializes in heart rhythm disorders, says that anyone who faints with a family history of other members of the family having been lost under the age of 50, from sudden death, should be assessed. The key is identifying the condition.