What should I avoid before a myocardial perfusion scan thallium scan cardiac nuclear imaging?

Caffeine. You should avoid caffeine and beta blockers, just because they interfere with the test.
Caffeine. As the clinic for specific details, but in general no caffeine for 24 to 48 hours, no blood pressure medications for 24 hours, and no nitrates for 24 hours. Some clinics will have you continue your medications up to the day of the test, so check with them.
Coffe tea chocolate. If you have a pharmacological stress test such as adenosine, Dipyridamole or lexiscan, you should avoid coffee, chocolate, tea, "brown" colas and aminophylline- containing medications for 12-24 hours before the test because they contain caffeine, an "antidote' to the test. If you have a treadmill stress test, betablockers should be stopped with the approval of your physician.