Yes, Gratham Hospital has the best Cardiac doctor. My girl had cardiac problem at birth and got an operation when she was 2 months. Everything goes fine and my daughter is now 9 months. Besides, I think private doctor is over-charge when he is a specialist. Better go to public hospital. By the way, my daughter only waited for 2 weeks to have first appointment.
My baby also had this problem when she was borned and I cried always for her having this kind of cordiac problem and I had been checking via The Prince of Wales Hospital. Very luckily that the hole with 3mm size was disappeared when she was 10 months old (now she is 1 year old) So, please don't worry too much cos the hole will be disappeared as your baby grows up.