I is somewhat difficult to answer this question with the provided information as it depends a bit on your condition. It sounds like you had surgical correction for some sort of congenital heart disease. If you are fully corrected, then it is likely fine for you to go on rollercoasters though this may not be the case if your correction required shunts, etc. I would recommend that you discuss this with your doctor who knows your medical history.
I wouldn't ride on those rollercoaster especially with a heart condition, even if is in the past you need to take care of your self, ask me i have ride on those crazy rollercoasters from six flags or other theme parks, and the drop feels like ur stomach goes to ur heart, and your heart feels like it drops, is a weird feeling...