Suggest Remedy For Pain And High Heart Rate

Was working out on elliptical with a heart rate monitor...after about 20 mins of my heart rate being around 150, my heart rate shot up to 191 and I could feel my heart beating rapidly. There was not any pain associated with the sudden increase. Within 30 seconds of stopping my exercise, my heart rate was about 130. Is this something which I should be concerned about? I am 45 and just had a stress test about a month ago with 95 percent efficiency.