Toprol should help lower you BP and your HR, I assume it does.
I think Toprol is usually not effective with atrial arrhythmia, such as AFib, which I have. I'm not sure what Atrial tachycardia is, but assume it is different than Atrial Flutter or Fibrillation.
Many people have mitral valve prolapse without any serious consequences, but I think it needs to be check on, such as an echocardiogram, every few years, perhaps 5+ years is sufficient. Have you had an echocardiogram? How was the prolapse diagnosed?
The HR of 100 isn't particularly troublesome in my mind, high but not enough to be worried about, but the BP is too high. Maybe you need a higher dose of Toprol, what are you now taking? I take 150 mg a day of the generic, and it holds my HR in the 80s to 90s when at rest. My blood pressure is normally acceptable, so it is on the low side with the medication.
I made a mistake my HR was 159 at rest was not 100. Echocardiogram showed several leakages and confirmed the prolapse. ECG showed pvc's. and atrial tachrcardia. I am on 100mg a day of generic form of Toprol.
I consider a rest HR of 159 too high, it needs to be lowered. If you're at 100 mg of Metoprolol a day it may just not be effective for you. I take more, 150 mg, and still have a high HR, but more will push my BP too low, makes me dizzy. Makes it hard for me to get up from a seated position without some dizziness. I tolerate 150 mg much better, my rest HR seems to run in the 90s...can be low 100s. This has gotten worse over past days, maybe I'm eating too much chocolate :) My walking around HR tends to be in the 120 range. I can't exert myself or it will get too high, greater than 150 from my age is too high.