Minimum / Maximum Heart Rate

I have a heart condition, arrhythmia, which is quite common. It's getting less frequent as I get older. Sometimes my heart beat skips about and sometimes it races; once it jumped to 240 when I was cycling with a heart rate monitor on and yes that did feel pretty odd and scary. My normal max heart rate at that time was 200. I can usually get it to stop racing by pressing on my eyeballs or pinching my ear lobes; seriously. Something to do with the parasympathetic nervous system or what have you, I wasn't paying much attention to the doctor after he told me it wasn't likely to kill me.

Tell me more. I've had this feeling before, where my heart feels like its racing. I've just never had my HRM on at the time. It generally stops after a few minutes.