Heart Rate During Crashes

I have moderate CFS with episodes of being severe. On days I have moderate CFS symptoms, I have very bad stomach issues, light and noise sensitivity, cough, sore throat, shortness of breath, POTS flare ups, chronic pain etc. My resting HR during these times is usually about 85-90.

However, when I dip into severe CFS, which I consider to be when fatigue is the most predominant and overwhelming symptom, making me mostly bedridden, my other symptoms usually reduce and my HR dips to about 70bpm. It's not unusual for me to sleep for more than 20 hours a day during these times, which can last up to 4 days.

Does anyone else have similar experiences to this? Everything I read is that people get higher HR during crashes. Mine only gets higher when I am fighting an infection or virus (which unfortunately is very often).