What Causes Extreme Dizziness, Nausea And Slow Heart Rate?

My future daughter-in-law who is 27 years old just started experiencing extreme dizziness, nausea and low heart rate in the 40s. They were unable to find what is causing these symptoms and let her go home after an overnight stay last night. She had a Cat Scan, blood work, x-ray of the lungs, a med to try and bring up her heart rate but it didn t do much good. Her blood pressure and oxygen levels were fine. She isn t any better and they just sent her home.