Question: I have been having intermittent episodes of shortness of breath and tachycardia/palpitations for over a year. (My resting heart rate is normally 60s but it would elevate at different times) I was seen by pulmonology and the only thing they found was a low DLCO. I had many cardiac tests and the only thing they found was a flat blood pressure response during stress/exercise tests and an exaggerated heart rate response. For example: When I would go up 2 flights of stairs my heart rate would go from 70s to 130s. Sometimes even higher. So they started me on Acebutolol. It is definitely helping with the palpitations. I barely feel my heart beat, when before I could feel it a lot through out the day. However, now when I walk up the stairs I no longer feel my heart beating through my chest, the rate only goes up a little bit, yet I feel horrible! I feel lightheaded, dizzy, shortness of breath and have chest tightness. (I had some of these symptoms before the acebutolol but they seem even worse now-I thought it would be the opposite.)

So here is my question: Could the acebutolol reduce my cardiac output causing me to feel this way?
None of my doctors have been able to explain why I have such an exaggerated heart rate response when going up stairs or an incline. I used to work out regularly including the stair climber, so why now is it so hard for me to do? And why did my heart rate go up so quickly with minimal exertion?