I know only time-of-flight, but luckily we have Google, right? (hint: next time write full term, unless you’re sure that everyone is familiar with the abbreviation).
http://en.wikipedia.org/wiki/Tetralogy_of_Fallot
At least it explains the blue kid…
The wiki doesn’t specify, whether is it dominant or recessive disorder. In the first case the cause would be random mutation passed to your baby, in the other you had to be both carriers and your baby got unluckily the allele from both of you. I would bet for the second option.