Suggest Remedy For Tightness In Chest And Shortness Of Breath

My husband for the last month has been having tightness in chest burning breathing and shortness of breath when exerting himself as well as problems with his erections. All vitals show fine. Lungs good and echo ca rdiogram came back good. His doctor thinks symptoms ate not heart related. We still have the option of a dye test to check for blockages. He is receiving plavex a nitro patch a pill to keep heart Tate steady and lipitor. He couldn't complete stress test and only can walk at slow pace without increasing his symptoms. When given nitro spray it alleviates the burning and tightness but only for a few hours. If it isn't the heart then what else could it be