I think the usual comment about structural issues applies to ventricular arhythmias rather than SVT, but I could be mistaken. SVT is a abnormal rhythm that originates above the ventricles and I have heard doctors use different terminiology in this area. For a pretty good description of SVT, check out Doctor Patrick Chou's webpage at the cleveland clinic website. The doctor has a video posted that describes atrial tachycardia, afib, SVT, AVNRT, and ventricular arhythmias. I must say this doc does a great job of explaining a fairly complicated topic in a way that newbies can understand.
When I still had my SVT, my heart rates went up to 250bpm, and i felt a little light headed, but never afraid. Some SVT's can be fixed with a high success rate; maybe you could ask your doctors if or when an ablation could be an option for you?
".......Is it important that I know what kind of SVT I have? "
I think it is difficult for a cardiologist to determine what kind of SVT you're experiencing except for perhaps Wolf-Parkinson-White syndrome as that leaves a telltale EKG signature when in NSR. So the fact that they aren't telling you what kind you have is most likely because they don't know if it's AVRT or AVNRT or perhaps something else. Both produce the same basic results. I'm not an expert but I would think that because AVRT is an accessory pathway and typically located away from the AV node that it would be easier to eliminate (This is the type that I had). AVNRT on the other hand involves a reentry circuit within or just adjacent to the AV node. These pathways are formed from tissue that behaves very much like the AV node, and in fact some physicians regard them as part of the AV node. AVNRT is five times more common than AVRT, so the odds alone favor it being that. AVNRT also favors females in 75% of the cases of SVT.
While your heart may be displaced, and otherwise oddly positioned, that doesn't mean that it is not structurally sound, and I think this is perhaps what they meant when they informed you of the results of your echo.
You'd think that having SVT nearly all of my life, six to sixty until getting it fixed three year ago that I'd be used to it; a thousand episodes maybe? I don't really know. But each one was anxiety provoking and I always felt that this was THE ONE, the one that I either couldn't slow down, or the one that was going to get me. I'd have them three to five times per month, and towards the end, they were coming not when I was active, but the opposite. I'd be driving home from work on the interstate. Who was going to help me if I needed assistance? Perhaps I'd be dining with my wife in a nice restaurant. Would I make a scene trying to sow it down? Mine required intervention in order to slow them. I had a very stable and reliable accessory pathway, so once it started up, it was self sustaining, running on and on for minutes.... hours if I had let it. But each one caused angst even though each one was successfully converted all of my life. It is perfectly normal to feel this way. But understand that if you are young and reasonably healthy, that it isn't going to harm you and it will not cause long term effects on your heart.
As for your medication, 50mg per day is a rather low dose. At one point I was on 200mg per day although I'm currently on 75mg mainly as a prophylaxis. I don't know why they are easing you off of it. When I had my electrophysiology study, I was told to just stop taking it prior to the procedure. There was no "withdrawal symptoms" or rebound effects. Metoprolol has an approximately 5 to 7 hour half life, so it's eliminated from your system rather quickly.
By the way, I believe the term AT and SVT are both atrial arrhythmias. But I believe they can be different, although I've read that SVT has replaced AT.
I hop you can get your problems worked out. Cardiac ablation was very successful for me as well as many other who have passed though this forum. Just remember that if you see problematic stories of ablation, it is because those have come here seeking help while the successful ones have moved on. With a success rate in the ninety-plus percent range, odds are in your favor should you ever decide on getting your SVT fixed. It is undoubtedly much less painful than what you've most likely experienced with surgeries for you PE. Best of luck!
Thank you both for your replies. I was on the lowered dose for about two months and then this past weekend I had a couple 'episodes' which were a bit confusing as the sensation was slightly different as to what I experienced pre PE surgery. Before my pulse would be extremely faint but it was just pounding away last night and I could hear it in my ear. It woke me from a sleep which is TERRIBLE. I woke up to that familiar surge and it shot off and just rattled my whole body :(..... Ugh! I hate the feeling. For me it is just terrifying which I know just makes it all worse. I become very scared that I'm going to die and leave my 2 1/2 year old behind. I know that SVT is typically harmless but it never feels like it. So I now have an appointment to see a cardiologist to discuss the next steps.