No caffeine, no smoking it all has to do with your heart rate blood presure,and ekg. Tomorrow if your walking the treadmill no caffine after midnight I tell my patients.Also nothinh to eat or drink 2 hours before your appt.If your not walking the treadmill caffine is bad if you are having a chemial stress test using persantine,adenosine,dobutamine because you may have reaction with the medication they will inject to speed your heart rate up as if you were walking.Make sure you tell the Cariologist how you feel at all times if you are feeling any sob ,chest pain or fatigue so your dr can document how you are feeling.Cardiologist, and ekg tech will be monitoring you the whole time. Hope I could help nuclear medicine tech asst.