I'm not terribly informed about these types of issues, but is it possible that all the exercise you do is stressing your heart too much?
Yes, I am sure that over the years the intensity of the training has stressed my heart. I'm fit but I would imagine there's also been damage that has occurred, and I already know that my heart is a lot larger than an average person for a start.
...you mentioned that you recently got your heart rate up to 196. To me, this sounds like maybe unnecessary stress on your heart that it's not in the mood to handle right now, but again, I'm not really an expert.
The 196bpm was actually from the exercise test I did with the cardiologist last month
The highest I have ever hit in training was 191. If I'm honest I feel pretty comfortable and in control right up until my HR gets into the high 180's (as in I can still hold a conversation); the cardiologist told me that I simply have a high aerobic threshold which is probably why I can hold a fast/hard pace for a long time.
I'm back into the training again now (powerlifting rather than the endurance stuff), but I'm definately aware that I need to be careful. Just to put things into perspective, the cardiologist explained to me that during a 24hr Holter Test an average person would typically have 500-1,000 ectopic heartbeats. During my 24hr test I had over 18,000