Originally Posted by scottfsmith

If its not killing a lot of people it is unknown to cardiologists... the primary focus of the field is on avoiding death since a whole lot of people die from heart issues. These days individuals are getting a lot more data from their HRM etc so are much more aware of all sorts of often minor glitches that can happen. I personally have a strange thing where my heart will sometimes just bump up 10-15 bpm from where it "should be" given the effort I am putting in. And sometimes it bumps up even more, and then I get that "not well" feeling and ease up. It usually happens about 10-20 minutes into the activity. Too much sugar/caffeine and/or lack of hydration are usually a factor.