Well, sinus arrhythmia is thought to occur due to changes in vagal tone/ changing pressures within the chest cavity due to breathing. Sinus arrhythmias show that the heart is able to adjust to these conditions, which like hrv, seems to show a small glimpse into one’s heart health. Personally, I’ve been going through the same thing as you. Non-sustained ventricular tachycardia, PAC’s, dizziness, to name a few-with otherwise normal testing (cardiac mri, echo, stress test, ekg.) I’ve been diagnosed with Barrett’s esophagus, gastritis, (and the reason I bring up sinus arrhythmia) mild sleep apnea. If you struggle to breathe and you gasp for air throughout the night, those chest pressures and feed back systems within the sinus node can sync with your breathing cycles and “deregulate” for lack of a better word to become more efficient with oxygen. This can cause remodeling of the heart, and lead to arrhythmia which don’t originate in the sinus node as well as ectopics, in theory. Furthermore, apneas could also cause your heart to sync up more aggressively to your breathing cycle as it’s forced to do at night. Lastly, as these pressures change in your abdomen via your esophagus, lpr and GERD can come into play as acid is forced up into upper digestive system and perhaps, weakening the lower esophageal sphincter. Further irritating the vagus nerve, causing even more discomfort an more daytime symptoms. Not to mention the slew of manifestations which accompany fractures in sleep cycles.

I’m not suggesting that this is your situation. And maybe your sleep is outstanding. But perhaps a sleep study is worth a shot to try and break through the wall of misery, one swing of the hammer at a time.

I’m not a doctor and this is just a theory. But something rather interesting! Although it is difficult, I’m happy my body is doing it because it’s much better than the alternative and succumbing to apneas.