How likely is long qt syndrome to kill me?

Not super likely: Long qt syndrome (lqts) is a congenital heart defect that may result in syncope and lead to sudden cardiac death, which usually occurs in otherwise healthy young individuals. Lqts is thought to cause about 4000 deaths in the United States each year. The chance of someone dying from this is approximately 6% by the age of 40 years. (from medscape's emedicine).

Unlikely but: You should have regular cardiology follow up and follow all recommended precautions.

Long qt : Depends on the type of genetic defect you have and several other factors such as the degree of QT lengthening on your ECG