Hemodynamics in ME/CFS and POTS

New Research

van Campen, C. (Linda) M. C., Rowe, P. C. & Visser, F. C. Two Different Hemodynamic Responses in ME/CFS Patients with Postural Orthostatic Tachycardia Syndrome During Head-Up Tilt Testing. Journal of Clinical Medicine 13, 7726 (2024).
https://doi.org/10.3390/jcm13247726

• Published on 18th December 2024
• Retrospective, case-controlled study
• 507 ME/CFS patients, 233 ME/CFS plus POTS patients and 48 controls
• Evidence for Pathology
• A team of prolific ME/CFS researchers: van Campen, Visser and Rowe
• No external funding, no conflicts of interest, no open data

Headlines

• People with ME/CFS plus POTS with an end-tilt heart rate delta of <40bpm have postural tachycardia at the pathological end of a common physiological spectrum, namely the inversely proportionate relationship between heart rate (HR) and Stroke Volume Index (SVI)*.
• People with ME/CFS plus POTS with an end-tilt heart rate delta of >40bpm do not show the common physiological relationship between HR and SVI, and therefore have another, or an additional, pathology.
• ME/CFS and ME/CFS plus POTS <40bpm groups have lower Cardiac Index (CI)** when upright than healthy controls. The ME/CFS plus POTS >40bpm group did not; their hearts are working much harder.

*Stroke Volume Index (SVI): a measure of the volume of blood pumped per beat/stroke.

**Cardiac Index (CI): a measure of the volume of blood pumped per unit of time.

Review

People with ME/CFS plus POTS (ME+P) can be categorised into either >40bpm or <40bpm heart rate groups, referring to the difference in heart rate at the end of tilt testing.

Healthy Control, ME/CFS, and <40bpm ME+P groups showed a linear decrease of Stroke Volume Index (SVI) with increasing heart rate (HR) at end-of-tilt; since this relationship is observed in healthy controls the results suggest this <40bpm ME+P cohort has postural tachycardia at the pathological end of a common physiological spectrum.

Graphically, the gradient of the SVI-HR relationship was similar between these three groups, but both ME/CFS and <40bpm ME+P groups had reduced SVI even at low heart rates (lower y-intercept) indicating reduced baseline cardiac output when upright. Results in the study directly show both groups had lower Cardiac Index (CI) when upright. It is hypothesized this was due to reduced preload, i.e. insufficient venous return, or "venous pooling."

The >40bpm ME+P group did not share the normal physiological link between SVI and HR when upright, suggesting there is another, or an additional, pathology at work. These patients had very high heart rates when upright, and high stroke volume, and therefore even higher cardiac output than healthy controls! It might be tempting to label this group as hyperadrenergic, but adrenergic markers were not assessed in this study and there are other pathologies that could also be considered.

Overlap between ME/CFS and POTS is clear from the shared symptomatology and recorded comorbidity. Is some of ME/CFS actually POTS plus heart failure? Is there a common pathology between these two disease entities? We should take care not to confuse our map for the territory.

The authors have a great history of research in ME/CFS and POTS. Special thanks to them for collecting and analysing this relatively-large dataset.

Thank you to all of the patients, families, doctors, healthcare professionals, scientists, engineers and everyone else working to understand and improve the lives of people with POTS. Please join and subscribe.