Prayers Please

Please say a prayer for my dad.
He was one of the very first patients to undergo reparative surgery of a congenital heart condition called Tetralogy of Fallot. His surgery was performed on a small group of young children by a visiting surgeon from Europe. He was one of a handful of survivors of the surgery.
He was scheduled today to have a cardiac valve replacement surgery, and has had some complications surrounding the procedure and in the postop period. It is a very scary time for our family. Please keep him in your prayers.