Closed heart in baby

My 4 months old baby has been sneezing and coughing for few days so i took her to the dr. She said she has infection and prescribed saline drops. While checking the baby she said she heard something and told us to go to the heart specialist within 2 weeks. When i asked for explanation, she said, her heart seems closed, it's very common and babies are born with closed hearts. Nd they open up on their own. But it's better we get it checked. I was not satisfied with this explanation.. We live in germany and dr's English was not as good. I have been really freaking out ever since we have seen her dr. Has anyone experienced this and can explain it to me? ☹