my daughter 8.3 years had psvt, suggest me further...

Try natural potassium sources, such as organic bananas (the regular ones are too high in sugar), white mushrooms, potatoes (baked), organic blackstrap molasses (tbsp) are good in hot water.  Bananas always work for me when I feel the problem coming on.  If you get those in her as a reactive & then increase them in her diet as a preventative.

Also, to help the tachycardia episdoes , since she is young the valsava maneuver might be a little difficult, I prefer coughing anyway, works better for me.  Splash cold water on her face too.

Outside of these you need to find if certain foods are triggers for her and remove them from her diet.  Avoid sugars (processed foods, sweets, etc.) and anything with caffeine, especially chocoloate.

I am on top of my SVT (which I've had since birth) by switching to a strict whole foods diet high in organic veggies, exercising a lot, abstaining from coffee & alcohol, and avoiding high stress work.  Because of this approach I am off the meds and delaying (and hoping never) surgery.

Can't stress enough to try the whole foods diet approach, which is high in organic veggies.  There's lots of success stories out there.  

Kirteesha, I too have this problem but mine was so severe if I hadn't had an ablation I would not be here today it helped tremendously considering I was sleeping 20+ hours per day but I agree it should be last resort if possible would also highly recommend mayo in Rochester MN. I have never been back to normal but have found triggers that I have learned to stay away from the biggest ones being chocolate and msg..especially Chinese food. I also found that metoprolol was not effective in my case as it lowered my bp to dangerous lows and 12.5 is a pretty high amount. Just always stay educated as this will be a life long journey

Chrisfox, that's so neat that eating whole foods as helped you.  I had my first SVT almost a year ago now.  Was having a lot of them but I went on metoprolol and I rarely have them now.  Interesting you mentioned potassium.  I had wondered if perhaps low potassium could be causing mine.  The first time I had a SVT they took me to the ER and did bloodwork. Potassium was in range but just barely. It was on the low end.  The doctor's didn't really think it could have been low potassium though that caused it.  They said that high potassium would more likely cause tachycardia than low potassium.  Anyway, I eat a low carb, whole food diet but I wasn't eating potatoes or bananas back then but I have recently been eating green bananas daily in a smoothie.  Sounds weird I know but it's a good form of resistant starch and it won't spike my blood sugar because they are green.  However, they do still contain potassium.  I am thinking of weaning off the metoprolol but my doctor said if I do they SVT's will probably return.  So I am a little scared to go off it.