I have had three episodes now during the middle of the night that are terrifying. (One was just while laying around) Out of a dead sleep I will awaken and my heart is racing so fast I can't even count the beats. I start trembling and shivering and feel very weak. The first time it only lasted about 5 minutes. Last night it lasted almost 30-40 minutes before it would slow down. I was so close to going to the ER, but was afraid the minute the ambulance showed up it would be normal again. I had heard if you hold your nose and mouth shut and try to blow that causes your heartbeat to slow down...well that didn't work...Finally I decided to take a xanax and within about 2 minutes it slowed down. I can't believe the xanax worked that quick, but after that I was ok and could go back to sleep. This morning I awoke and feel like I have run a marathon. Very shaky, weak feeling and tired. This was so scary and I'm afraid it will happen again, but next time my husband might be out of town and I'll be alone. I don't want to seem like a hypochondriac and run to the ER every time this happens but it really has me worried. I had a dr. appt last week and mentioned to him about the one when I was laying around and that it only lasted about 10 minutes and he said it was probably just an adrenalin rush, mostly because I do tend to have anxiety problems to start with. What would cause this while sleeping. I had no problems before going to bed. How could anxiety bother you while sleeping? I had worked in the yard earlier in the day and really pushed my heart rate up for a few minutes and had to go lay down and rest for a minute, but after that felt fine. Could the exercise earlier in the day had caused this 12 hours later? Can adrenaline really effect you in this way with rapid heart rate and palipatations versus being a true heart problem? Sorry for all the questions, but I am so scared it's probably adding to my symptons now. Please don't just tell me to go see my dr. He thinks I'm a head case now as it is. These are true symptons and it's not all in my head. Thx for your advice.