I had severe episodes of AFIB for years. Then READ in a news column written to a DOCTOR, who had same symptoms as mine and HE said SOME people are EXTREMELY sensitive to caffeine and CAUSES heart rythm problems. in them. I had been drinking 4 cups a day, and I decreased to 1/2 cup and it caused problems with that amount. After ELIMINATING, I have no problems. I used to have episodes lasting for a few minutes to all night long. That was when I was 21. At age 75, I started to eat some coffee ice cream made in the US, and boom I had an episode. I mentioned Mountain Dew because some people do not know it contains more caffeine than colas. I don't care what the evidence says. I know what causes it in me and the DOCTOR said the same. Before quitting coffee, I tested it over and over because I did NOT want to give up my coffee or coffee ice cream. The night I had serious arrythmia, I had eaten only 1/4 cup of coffee ice cream and two small pieces of dark chocolate.