My daughter age 20, had a bad headache, then blurred vision, then she's blacked out for about 5-10 minutes. When she woke up her speech was slurred a little. She also complained of chest pain. This has happened twice, about a week apart. Took her to ER both times they did EKG and CT. Everything from blood to urine was ok. CT showed nothing. EKG showed slightly low heart rate. Her family doctor got us an appointment with Cardiologist and Neuroligist, appoint. In two weeks. What could this possibly be? Is it serious? Life threatening?