What exactly is torsades de pointes? how many percent of patients with tdp die? how many percent of (female adult) patients with persistent prolonged qtc interval range of 475-505 would ever see tdp occur?

It is an abnormal fast beat of the lower ventricles of the heart and has many causes. Uncorrected' it can cause cause strokes heart attacks and even death. The exact answer to your last question cant be given as there is no study specific to that

I would go to uptodate.com and all about it and then see cardiologist who can get more details and look at your family tree and EKG. Get detailed family tree on sudden death and other heart problems.

I agree that consulting a cardiologist who's a electrophysiologist would be helpful. If you have aQTc that's only borderline prolonged( about 440-450) and you have no significant personal or family history, the chances of torsades is very low. Some EP labs can do genetic studies to determine the presence of long QT syndrome.