Hi
Welcome to the MedHelp forum!
I am really sorry to hear about your daughter. Infection, poor blood supply, low oxygen (most possible cause due to her heart ailment) can all cause the hands to become cyanosed and appear cold and purple black. I pray God gives you strength to deal with this loss. Take care!
Myocarditis can lead to sepsis and shock. As the peripheral vasculature shuts down, the tissues of the feet and hands will turn purple and then black, It is very common in cases of sepsis.
What could cause your hands and feet to change colors?