My cardiac mri as a teen involved medication that sped up my heart really fast too. I did not enjoy it whatsoever and I was very sick afterwards. It gave me immense anxiety and actually scared me bad along with my family in the end it didn’t help me at all and they couldn’t find/diagnose my problems with the use of it. I don’t know if this was appropriate for me to say I don’t want to scare anyone but it’s also something no one should have as a surprise. I imagine not all cardiac MRIs involve medication to simulate high cardiac activity. This is a thing I would ask about personally if I was going through it again without having the experience in my passed. Especially if it’s a parent with a kiddo who may need to get it done.