My Dad Is Having A Procedure Done Where They Insert

My dad is having a procedure done where they insert a scope at his hip all the way up to his heart to find out if another procedure will work to fix water retention around his heart and I am trying to figure out what the diagnosis is called and how serious it can be. I feel he isn't telling me so that I don't worry. He said it's hard to breathe and he has to take water pills to reduce the fluid.