With my PAC's,there's not much of a pause after. My PVC's bump harder and pause longer. I still take 100mg. Metoprolol daily, but it does squat for them. I still take it mainly for BP control, and for heart attack survivability, but that latter fact is now in question. I hate to be the prophet of doom, but don't be surprised if the higher dosage is ineffective in quelling them.
For me the pacs feel more like blips and the pvcs feel more like fizzles. The difference being I don't have much of a pause with the pacs but do with the pvcs them being more noticable when my heart rate is slower. I do rather surmise, not being a doctor I can't say for sure, but I kind of think pacs/pvcs and svt feed off each other. One gets the other going and vice versa but I also truely believe that stomach issues, especially acid indigestion plays a fairly big role in the errant beats. I might try taking some over the counter antacids like tums or other chewables and see if it helps calm the pacs/pvcs down. It worked for me. If it does then I might ask your doctor if it was ok for you to keep taking them. But do a test first to see if it helps considering it seems like the beta blockers aren't helping much. Though I do think you also have to give the medicince a little time to work. I have never been on bbs but maybe others who have can give you a time frame of expectation for the medicine to reach full strength.