Accelerations & decelerations in heart rate

I was diagnosed with SVT and put on Metoprolol twice a day on Feb. 22.  For 10 days all my symptoms seemed to go away.  Then, Wednesday I began to feel irregular heartbeats, chest discomfort, and fatigue.  On Saturday, I felt really fatigued and greater discomfort, so I got out my sport watch heart monitor so I could monitor my heart rate.  For 3 hours my heart rate would go from 60's to over 200 beats a minute, then down to the 30's or 40's.  The time in the 200s would be brief--5-10 seconds.  The recovery time from the 30's or 40's took a few seconds longer.  For a while the episodes occurred as often as 3 times a  minute.  I never felt the accelerations or decelerations themselves, just felt fatigued, chest pressure, and "yucky".  I went to the ER, but had my last episode while I waited to be seen.  I did have a heart rate in the ER that kept going under 54 bpm and kept triggering the monitor alarms.  I was kept on O2 the entire time I was there.  The ER doctor put me on a Holter monitor for 48 hours, but I've had few symptoms.  He said there was some heart condition where the heart rate would go from high to low extremes, but didn't tell me what it was.   So, has anyone else ever experienced this?  Is it just a weird form of SVT that I'll have to learn to live with?  And how should I deal with it when it happens?

[Encephalomalcia]

There is a beta blocker called coreg that blocks more than the Metoprolol will.  Ask your doctor if Coreg is right for you.