I developed sudden heart problems year and a half ago and haven't struggled with exercise before that. Feels like heart is "turning over", "flip-floping" and ov

I developed sudden heart problems year and a half ago and haven't struggled with exercise before that. Feels like heart is "turning over", "flip-floping" and overall does not know how to contract properly (lasts from a moment to a few seconds, but quite frequent). This also happens while resting and even asleep, which wakes me up. I still exercise regularly (brisk walking, cycling at <= 130 BPM) but anything more intense makes these sensations almost unbearable. It's just fascinating that people can live to 80 or more and still be moderately healthy and physically fit enough to run as this guy in the article, that's all.