Have the "skipped heart beats" too - mostly when stressed, and they can be very annoying. I deal with them by realizing that they will not cause a heart attack, and won't kill me. Sometimes I do the opposite of what you did - rather than go sit down I go do jumping jacks or running in place to prove to myself that it is safe! Lately there have been some very stressful situations in my family and my heart did a lot of these flip-flops. There is rarely a day when I don't have some of them. Our nerves can play some very mean tricks on us, and that is just one of them. Relax and just let them happen - ignore them if you can. Even when you think things are fine, your subconscious can dredge stuff up and put them to work.
Scaredy Cat always has good advice
Chill out, and have a good weekend. I'll try to do the same.