Toprol-XL and long periods of time

I have been taking Toprol for about 2 months for SVT. I have noticed that I am tired especially of late I get tired during the day or if I have to sit for long periods of time I may doze off. My heart beat is slow and I am not able to increase it during exercise which means I have gained weight and have swelling in my lower extremities.

However, I still have the SVT usually before and after my menstrual cycle. I could be pre-menopausel. I'm not sure yet. I had one cardiologist want to do the ablation but this was after my potassium levels and sodium levels werer found to be off quite a bit. Once I was removed from the diuretic I was taking for my blood pressure (Family Practitioner did this) my levels became normal. I had been on that medication for years and then this just happened. Supposedledly, the low levels made the SVT more severe to the point that the vagus manuevers wouldn't work.

The Toprol appears not to have any effet on my BP or the SVT.