What tachycardia did you have? Sinus tachycardia? What other tests and exams have you had done?
I don't think Metoprolol makes them worse. What I have seen on myself, however, is that it doesn't work at all. I took up to 50 mg a day. I switched temporarily now to Toprol XL to see if that's the answer since the generics seem to have no effect.