I am tired a lot, although I think it's more due to my lack of sleep. As for the elevated heartbeat (tachycardia), I have the same issue and was placed on medication for it. Once it didn't help, I was referred to a cardiologist. After getting a clean bill of health heart-wise, the cardiologist told me that he feels it's due to the constant state of pain, that it's just so hard for the body that the heart races. He said it's okay for now, but that long-term, it can wear the heart out prematurely, which is why we're working so hard to get the pain under control.