CTA

Hi,
Has anyone ever had a CTA? I have one Tuesday and I am scared. They are turning my pacemaker down to 57 and I have to take beta blockers for 3 days ( i have not yet taken them yet..too scared to I guess).
They say they need my heart rate at 60 not any higher for the test. Well I know how I feel with my heart that low.
I would like any information from anyone that has taken beta blockers for the test only and had to have ther pm turned down,
I will take any information from anyone:) Thank you
Amy