Tachycardia when standing and moving around

[Shandyp2511]

I have Mitral Valve Prolapse and a couple of months ago, I was put on metoprolol for Tachycardia. I am only taking 12.5 mg because it was bringing my bp down. Holter showed 154 bpm. I had been getting dizzy spells at work and my heart was racing a lot. After I was put on the medication I’ve been paying a lot more attention to my heart rate. It seems that when I’m at rest, my heart rate is fine. Usually in the 60’s or 70’s. When I stand and walk around it shoots up to over 100 even if just walking around my house. It’s especially bad when I first get up in the mornings or if I’ve been sitting for a long period of time. I stay on my feet for hours at work and I know that my heart rate gets up into the 120s or above just walking around. I’m not sure if the medication is helping at all at such a small dose but can’t take more because my bp stays below 100 a lot even with the small dose. I also have a lot of ‘head rushes’ pressure in my head when I stand up and disturbances in my vision. I can feel it in my body like it’s working hard to carry me around. I had these way before taking the beta blocker so I know it’s not that. I’m wondering if this could all be related or if anyone has experienced this?