I have the same problem when I smoke and I only take about 4 hits of medical out of a bowl... scares the hell out of me and I take a Xanax before.. sometimes a pepcid and an allegra or benadryl... I know it's hard but stay calm and relaxed.. hope this helps
AFter reading your post again I noticed that you said you have SVT attacks already. Are you being treated for the attacks or are they harmless? Anyway If you already heart rhythm problems I would bet that Smoking pot could aggravate the problem.
MM
Although I don't necessarily condone smoking anything, I used to smoke pot occasionally when I was younger ( I'm 35 now). Two kids and a marraige later, I have stopped smoking cigarettes AND marijauna. It's a personal choice. However, like you, I used to occasionally get a racey heart (tachycardia) after smoking marijauna. Tachycardia CAN make you very anxious and probably in your case the anxiety is causing the nausea. I did some research into this on the internet when it happended to me. I researched marijauna and Tachycardia. Marijauna can give you a temporary fast or racing heartrate. However, in healthy people (with no existing heart problems), the worst thing that your temporary racy heart will do to you is make you anxious. In other words,the temporary fast heart rate and anxiety will not cause you to have a heart attack or damage your heart. You dont have a heart problem just because Marijauna made your heart race. It also doesn't mean that it will happen if you smoke it again. However, it COULD cause your heart to race again and obviously you didn't like it so why try it again? Hope this helps.
MM