Thanks to all of you for answering me! I don't have a complete family health history, as I was adopted at birth, and have only found my biological mother. As far as I know there was no heart history on her side. I have never fainted, but I get vertigo a few times a year. So next week I will have a head CT as well as blood work and a repeat EKG. I will let you know what happens!
Thanks again for making me feel more at ease!
Some medications can also prolong a QT interval, so possibly looking at your medications (if you take any) would also be a good place to start. Of course following up with an additional ECG and having a good cardiologist figure out the interval by hand instead of just looking at the machine's reading would be warranted in this situation. Have you ever had any syncopal episodes or does anybody in your family have any problems with syncope or passed away from an unknown cause?
I don't know a whole lot about prolonged QT interval, but I do know that 490ms would typically place you in a high risk category. The QT interval is dependent on the heart rate of course; the faster the heart rate the shorter the QT interval. Today's computer-based EKG machines can calculate a corrected QT, but this correction may not aid in the detection of patients at increased risk of arrhythmia. No doubt your EKG machine spit out the various summary data, which listed the QT interval as "abnormal" Have you ever measured your pulse while at rest? 490ms would most likely yield a slow pulse rate.