Thank you for the replies. He is on beta blockers for the tachycardia - they regular his heart rate and blood pressure. He is also anemic, which obviously causes tiredness too - no known cause for that yet.

The hospital were aware of what drugs he takes when they put him on the beta blockers, and his shortness of breath. That isn't extreme, but is there on occasion.

So it's almost a damned if you do, damned if you don't scenario. I think too it appears to be a process of elimination - keep testing to rule out certain things. He is also going for a sleep apnea test.

I have to say that we have been lucky with his physicians and their treatment of him.

Good luck to everyone suffering from this horrible ailment.