What could be the reason for a prolonged QT?

Hello doctor,

I would really appreciate some advice on what to do. I am a 31-year old-female. About four months ago, I started experiencing bad anxiety and panic attacks. I went to a doctor for blood tests and ECG, just to rule out any health issues. In fact, I had two ECGs done three months ago. The first one was perfectly normal. The second one was done two weeks later. When my doctor got the results of the second ECG, he asked me if I was taking any medication. I said no and enquired about the reason for his question. He told me that my QTC interval was a little long on my recent ECG. He compared the two ECGs and told me he was not concerned at all. He has reassured me over and over again that I do not have LQTS (long QT syndrome) and that the QTC interval was just slightly longer on the second ECG. I want to believe him but I am so scared of possibly having it. I had an ECG done right after that, and it was fine. Should I get another ECG done? Or see a cardiologist or just believe my doctor? Please help.

Thank you.