Supraventricular Tachycardia (SVT) is a broad classification. I had about 10 episodes of 140 BPN over ten years with no more complications than emergency room trips for conversion or conversion at home with propafenone. My particular type was atrial flutter which appears to have been cured by ablation a little over a year ago. If your heart is otherwise healthy it is a condition that can be managed (but certainly no enjoyed!) https://en.wikipedia.org/wiki/Supraventricular_tachycardia
What type of svt do you have? Nothing really stops svt. It only slow the heart rate down when you have it. Reentry svts can be corrected with ablation. As for meds it really is a matter of what works for you. What works for one doesn't work for all. But accessory pathway svts won't go away without an ablation. Unfortunately there are other svts that are harder to treat so just listen to your doctor and keep trying to find what works for you. Take care.
You shouldn't be afraid of Metoprolol. It is widely prescribed and is well tolerated by most. After 5 years free of SVT, I'm beginning to show signs of it coming back, or perhaps early stages of A-fib. My cardiologist increased my dosage to 150mg. per day as I seem to be resistant to its effects.