I take a bb for inappropriate sinus tachycardia and neurocardiogenic syncope. When I started them at 1st it made me more aware of the tachy (before hand I didn't get palps with the tachy and so was unaware of it). By the 2-3 week mark I felt so much better. It actually took away my fatigue and increased my bp to a more favorable level (it happens to be low again, but ok). My ep said this happened, because my heart was pumping more efficiently now.
I have been on atenolol (Tenormin), but couldn't tolerate but 1/2 of the smallest dose, Cardizem, Toprol and am currently on bisoprolol. There wasn't really a problem that caused me to chg. bb's all those times, it was just... well, it's a long story.
I am allowed to take the xanax with my bb's. Oh, and my ep wanted to get my heart rate in the 50's, but said my heart wouldn't cooperate.