So,
as a part of the lyme community I tend to think CFS is only a symptom - not a disease by itself, like the scholar medicine wants to tell us.
Altough I like to look for studies labeled as CFS since I think in the direction, that a big portion of CFS is caused by ongoing viral or bactarial or parasitical infections. Therefore I like to look for "CFS Markers"
This study was already published back in 2006, but it shows a connection between the dysautonomia of CFS and a short QTc Time in the ECG/EKG.
Nothing to crazy, just for the ones that may wonder why there QTc Time is so borderline low (like me :> )
https://www.sciencedirect.com/science/article/abs/pii/s0022073605003316Results
In the pilot study, the average supine QTc in CFS was 0.371 ± 0.02 seconds and QTc on tilt, 0.385 ± 0.02 seconds, significantly shorter than in controls (P = .0002 and .0003, respectively). Results of phase II confirmed this data.