my accupuncturists showed me two pressure points which are useful for me in slowing the tachy. First one is on the sole of the left foot--about one inch below the pad below the toes...so it is about 2/3 of the way up the foot. Jam your thumb in there until the thumb hurts...and move it around.
Also below the palms of the hand there is a horizontal line--actually there are two but go to the highest horizontal line--go down two thumbs from it (thumbs are horizontal) and press in the depression there--in a massaging motion. This cools the heart. Start on left and do the right also. These are accupuncture/pressure points I find helpful.
If the ice is too much of a production you can just try splashing your face with cold water from the tap or fridge - you can do it more quickly than getting a bowl of ice and water together and it works just as well for some people.
thank you the ice sounds awful but i'll try it
(1) Carotid massage (ask your doctor how to do it or look up an explanation online -- this activates the carotid sinus which can slow the heart rhythm)
and
(2) plunging your face in a bowl of ice and water ("shocks" the vagus nerve so to speak which can help restore a regular rhythm)
Good luck!