Dear friend, I am very sorry to know about your father's death. Actually, bypass surgery
is not a 100% solution and even today inspite of so much advancement in the field of medical science a small failure rate still remains in all surgeries. We have to belive in luck factor also. May his soul rest in peace.... thats what I can say. Please do not blame doctor for this. The death is unfortunate but it was in his destiny.... god bless his soul.