I have been having heart tacacardia after I have ate ice desert and once after a mexican meal I drank have a glass of ice water.
Pluse jumped up to 110 and 150/54 sitting.
After this I was paying close attention to my heart rate. And found that I would drop a heart beat every 10 or so beats. No numbness or pain.
I know next to nothing about tachycardia, but I do know way back in college when I had a physiology class we experimented with heart rates under different conditions. We found it was normal for someone's heart rate to go up when his or her face was exposed to ice water. (We dipped our noses into bowls of ice water and just doing our noses alone raised everyone's pulse rate!) I don't remember how much our rates increased, but maybe what you've noticed is OK? -But I don't actually know with your condition if it is OK.
Mine dropped so drastically that my classmates freaked out thinking my heart was going to stop :-P ...that was painful. ..never..ever.. again..
do you hold your breath when you drink the cold water?
scroll down to Vagus Nerve Stimulation. It can also cause fainting.