Not this specific heart defect, but my oldest had a Ventral Septal Defect (also commonly refered to as a "hole in the heart") he was closely monitored and it did eventually close on its own. Since then, my second son has had close watching and has some sort of blurb on his pulmonary artery which is unexplained at this time.
Listen to the cariologist, try not to look at worse case scenario situations, it will make you crazy. That I do know from first hand experience. At my son's 2 year checkup, the pedi freaked me out because he thought the hole hadn't closed, thus sending me into a whirlwind of what if's and testing. In the end, it was deemed an innocent murmur, but that was a painful few months worrying my baby would have to undergo open heart surgery.
Do some reading, educate yourself, but also be aware of your reactions to what you read. if you find you are becoming obsessed with it, take a step back. Oftentimes these "defects" heal on their own or pose little significant impact as time passes.
My daughter had the same thing. They didn't pick up on the murmur until she was 18 months old and was seen by a different doctor. We were sent to a Pediatric Cardiologist, they found a hole in her heart as well. They told us to come back when she turned 2 it was still there, but not as big. If they see it is closing they will just monitor it and not jump right into surgery. We just went back after her 3rd birthday and it's completely closed now. So try not to worry, they'll just monitor it and go from there.