Hey Jeff,
My run of
PSVT can last a few seconds or several minutes ( seems like eternity when it happens).
It is SO much better now that I am on atenolol. I went thru most the calcium channel blockers meds to NO avail, toprol XL ( HATED it) and flecanide (worked well by my family dr freaked).

I only get the attacks now when I am really stressed, or I am very dehydrated/exhausted.
I also take tri salts- it is a magnesium, calcium, potassium powder you mix with liquid 2 or 3 times a day. It has helped immensely, especially in hot weather which is most of the year here in south Texas.
Also remembering what my cardiologist said helps me thru it... "You aren't going to die, you just feel that way!!".. comforting isn't it??