He just needs to be screened, at least blood tests. They can put him on a treadmill, but the only real test is a Heart Cath. Most won't schedule that unless there are other issues at his age such as high cholesterol, or family history. For my hubby the first sign was that his fingers would be really cold in winter and turn slightly bluish. For my mom, much older, it was her toes tingling constantly. Some have no warning at all. I wouldn't bet on a heart condition, but it does happen. There are many reasons, he just needs to talk to the doctor, and get some labs done at the very least.
If my dad and step dad at 73 can still have a healthy love life, almost anyone can. You just have to be honest, and try new things. Isn't it amazing what can be done now. I just can't imagine what men went through with early ED, in the old days. I am sure there was much more depression.
Can she schedule a consult with the doctor before he goes, to discuss her concerns for him. I know the HIPPA laws say the doctor can't tell her anything, but he can listen to her.