I would try not to panic and don't google, I know it's tempting to but I would say that slightly prolonged QT would not be long QT syndrome which you have probably come across when you've googled. I have had palpitations for many years from peri menopause onwards sometimes they are an absolute nightmare constant what feels like skipped beats and fluttering I was diagnosed with SVT's I have had a few holter monitors and they have come back having picked up the palps but my heart rhythm has been normal, palpitations are quite common in us ladies going through the menopause the fluctuation in hormones can cause them. My cardiologist prescribed me a Calcium Channel Blocker as because I have Asthma they don't prescribe Beta Blockers but for people who can take them I understand they are very effective.
If it's really worrying you get an appointment and discuss with your GP, did he make a comment at your appointment if not then he probably doesn't think it's significant when you get your holter monitor be sure to go about you're normal day, I'm sure everything will be fine
Take care