During my incident in the emergency ward, I was hooked up to an ECG. As I spent hours on end watching the ECG, I was surprised at my heart rate. In general, it was around 52 or 53. When I focused on it, I could get it down to 48 (at which point the numbers on the ECG all went red). I'm pretty sure that a year ago my resting heart rate was in the mid to high 60's.
Over the course of the afternoon, several nurses and doctors checked in on me. Several times, one would explain to the others "He's a runner." I guessed that that was to give them the context to explain my heart rate.
I googled "low heart rate" today. I have a condition called bradycardia. Basically, it simply means a heart rate lower than 60. It's completely normal for fit athletes (and obviously, that's the category I'm in ;-). "Too slow" is relative to your current medical condition.
I've been monitoring my resting heart rate each morning recently. An increase would indicate over training but I'm still consistently in the low 50's so I guess my body is managing to adapt to the ever increasing miles I'm running.
I've got bradycardia. And, that's a good thing.