Disclaimer/Edited to add - I clicked on your posts and it seems like you're older to cpaptalk than me, so possibly none of what I have to say is helpful. Is your O2 still dropping without any events? Did you ever get that figured out?
Original response -
your sleep charts don't provide flow rate so I can't tell what's going on at the times you posted heart rate increases.
My suggestion:
Have you thought about zooming in on the times you are seeing heart rate spikes and if there is maybe a narrowing/decrease of the flow rate or a micro-arousal at the same time? that's what I did. I have UARS though, not sure if you have that as well. with uars your airway is narrow to begin with and then narrowing while you sleep - which shows up as for me as the flow rate getting smaller and smaller until I jerk awake (but of course in no way remember doing so). UARS airway narrowing is supposedly a mild stressor on your body and brain (it sure as heck stressed me out though!), and the papers I have read say that with UARS your brain will micro-arouse a little to get you to widen the airway again, before it lets you go back to sleep. Thus why a lot of people with UARS don't can still feel absolutely awful, especially if that happens 100s of times over the night, but with no corresponding drop in oxygen so doctors are confused why they feel terrible. Another name for the event is respiratory effort related arousal or RERA.
and I find those little microarousals (which I don't remember) can jack my heart rate up a little bit. Not sure if they do for everyone, but they do for me. as opposed to when I have a full blown cessation of breathing and then my heart rate really jumps up.
Also, believe if you search papers /info on REM sleep - this site is very cool -
http://thebrain.mcgill.ca/flash/i/i_11/ ... p_cyc.html
, that they say that some heart rate variability is normal during REM stage, but as to what's normal heart rate variability, I am guessing it varies from person to person. Like if your resting heart rate is 80, maybe it's totally fine and normal to spike to 100; but if your resting heart is lower and you're an athlete, then maybe spikes that big would be a concern. If you do some digging on pubmed you might be able to find your answer for your specific heart /health issues that made you get a holter monitor in the first place. if you respiration issues / drops in oxygen without any events I've read that that can sometimes be a sign of brainstem issues?
Who knows how common or rare it is, but I found it fascinating when I learned about a woman Jen Brea who came down with a severe case of chronic fatigue. She made a netflix documentary about her chronic fatigue and other people who were similarly ill, and in her case, it seems like an improperly supported brain stem due to craniocervical instability (sometimes seen in ehlers-danlos, or other people with weak connective tissue) was the root cause of her issues. It took her 8-9 years to find a doctor who was willing to believe her and diagnose her and operate to fuse parts of her spine so that it would support her brain better and she went from being bed bound to years to now being quite active, able to sleep now, etc..
But I think she and some of the other people who had this craniocervical instability had symptoms of dizziness, POTS, random dropping of O2 to the 80s during sleep, and they were called fakers by doctors :/
ANyway, I don't know if that's what you're dealing with, but I hope you get help for whatever you are dealing with.
sometimes in order to succeed it just takes one more try. and a lot of frustration along the way.