Talk to the pediatric cardiologist who is going to interpret the c.t angio. Your child's echo might have revealed some problem which needs surgery and so before taking such a big decision a test to confirm the echo diagnosis is essential.at least 3 of my patients got c.t angio done at 1 yr of life and 1 was operated later.

There is a risk in every thing, Undiagnosed disease has more risk than the test, so go ahead