Hi,
My son was born with partial av-canal defect, which was repaired by open heart surgery at Boston Children's in December. He's doing great! He was 9 months old at the time of surgery and is now just over a year old.
We did not have an x-ray until around the time of surgery and then as part of the immediate follow-up during the days in the hospital after surgery. They diagnosed him at 4 days of age with and echocardiogram (basically, an ultrasound machine) and EKG, and continued monitoring him until the time of surgery using just these two measurements You might ask if these things could be done first since they might be able to get a diagnosis with just that. They will tell you if, for some reason, they think an x-ray is necessary.
Not all defects require open heart surgery and some murmurs are, in fact, innocent. But the sooner you get information, the better equipped you are to deal with things.
Good luck,
Laurie