My son was diagnosed with tetralogy of Fallot, is 8 months old.

My son was diagnosed with tetralogy of Fallot, is 8 months old and has never had any symptoms what so ever. From what Ive read this disease kills. I find it hard to believe there is anything wrong with my son, but I don't want him to go without a surgery that will save his life. The doctor who wants this operation misread the echocardiogram thought my kid was sickly then drags us down to get a better one done and after telling us he had three holes in his heart now tells us he has this other thing going. Which is understandable the equipment isnt perfect. But with this disease i feel like he should have mentioned how my kid could die within a couple years but he didnt. He didnt even act like it was a big deal he just wants to operate. So Im wondering about misdiagnoses or anyone with any experience with the disease who could offer their input. Thank you