It depends on: frequency, duration, and the actual rate. Oh, and how much it impacts your well-being as well.

a. If you are frequently experiencing SVT, it can seriously impact your sense of ease and well-being. It can interfere with proper rest, or even cause you to want to stop going for walks or cycling or hiking...which is never ideal, particularly as you get north of 75. If it's once a day, no problem. Three times a day, not really a problem....unless..

b. ..it's lasting for an hour or three each time, or you begin to fear it wants to persist and to continue in perpetuity;

c. if the rate is above 100 BPM, you don't really want that, not for long. Again, an hour once a day...a pain in the patoot, and it bears watching....but you won't die from that. Once your rate soars above 100 BPM and stays there for a total of two, three, six hours each day, or never seems to want to quit and to return to NSR, you should start thinking about getting an intervention from an electrophysiologist. In fact, once you have an arrhythmia, you should shake hands with a really good, highly sought, EP and get in line for a remedy that she/he can offer.

Bottom line with SVT, flutter, and atrial fibrillation, your heart can tolerate a lot of it for short periods...now and then. When the rate begins to soar reliably, and the frequency of events begins to climb, drugs are losing ground and your wonky heart's electrics are gaining it. IOW, these things tend to evolve, or to progress, to more intractable levels and persistence, and they get harder for the mid-level electrophysiologists to treat. Even the very top tier EPs will struggle to fix your rhythm if you go too long and your heart begins to develop other pathology as a result.

If your monitoring device ever says that you have ventricular tachycardia (and not just SVT), call an ambulance immediately, or get yourself driven to the nearest ER that has a great reputation for cardiac problems.