Hi

Thanks for asking.

Drinking very cold water can decrease heart rate by vagal stimulation, infact this is practiced in cases of increased heart rate in patients of supra ventricular tachycardia.

If your husband had a very high heart rate, it probably has nothing to do with the cold water, it needs checking to see what exactly caused this.

There may be a supra ventricular tachycardia with a very high pulse rate, holtar monitoring and some cardiac investigations are needed to reach a correct diagnosis.

Thanks.

drinking very cold water can cause change in heart rate by autonomous nervous system, it can be initial decrease in heart rate followed by increase, however each individual can respond differently , also same individual can respond differently at different times.
But in any case, if the change in heart rate was due to cold water then it must rapidly revert to normal, something like in 2-3 minutes,
if it lasts an hour or so then cause may be something else, also increased heart rate due to such normal stimulus will be not morethan 140-150/min.
suppose he had heart rate of 170 lasting for 5 minutes then it is definately abnormal. If such events repeats then seeing a cardiologist and getting a 24hrs holter monitoring done will be appropriate.

hope this helps