Comparison of the Degree of Deconditioning in ME/CFS Patients with and without Orthostatic Intolerance, 2022, van Campen & Visser

Background: Orthostatic intolerance (OI) is a core finding in individuals with myalgic encephalomyelitis /chronic fatigue syndrome (ME/CFS). Deconditioning is often proposed as an important determinant for OI. Deconditioning can be objectively classified using the predicted peak oxygen consumption (%VO2 peak) values as derived from cardiopulmonary exercise testing (CPET) and OI can be objectively quantified using cerebral blood flow (CBF) changes during tilt testing. Therefore, if deconditioning contributes to OI, a correlation between peak VO2 and the %CBF reduction is expected.

Methods and results: 18 healthy controls (HC) and 122 ME/CFS patients without hypotension or tachycardia on tilt testing were studied. Deconditioning was classified as follows: %VO2 peak ≥85%= no deconditioning, %VO2 peak 65-85%= mild deconditioning, %VO2 peak<65%= severe deconditioning. HC had higher %VO2 peak compared to ME/CFS patients (p<0.0001). ME/CFS patients had significantly larger CBF reduction than HC (p<0.0001). No relation between the degree of deconditioning by the %VO2 peak and the %CBF reduction in ME/CFS patients was found. Moreover, we separately analyzed ME/CFS patients without an abnormal CBF reduction. Despite equal CBF reductions compared to HC and large differences between these patients and the patients with an abnormal CBF reduction, cardiac index (CI) changes (measured by suprasternal Doppler) were significantly less compared to ME/CFS patients with an abnormal CBF reduction (p<0.0001) but larger than in HC (p=0.004). Despite these different hemodynamic findings, %VO2 values were not different between the two patient groups, argumenting again against the causative role of hemodynamic abnormalities in deconditioning.

Conclusion: In ME/CFS patients without hypotension or tachycardia there is no relation between the %VO2 peak during CPET and the %CBF and %CI reduction during tilt testing, whether or not patients have an abnormal CBF reduction during tilt testing. It suggests again that deconditioning does not play an important role in OI.

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Pretty interesting to see the significantly higher reduction in cerebral blood flow and that it wasn't correlated with VO2max (and in a relatively large cohort), but I think we need to see the CBF results replicated in a patient group that wasn't referred to a cardiology clinic, as these patients were.

 

I find it problematic that the authors define orthostatic intolerance as either hypotension or tachycardia. To my knowledge, orthostatic intolerance per se is a cluster of symptoms related to assuming an upright posture for some time, rather than findings related to heart rate or blood pressure. A real-world concern is that patients with OI symptoms but without HR or BP abnormalities may be denied disability aids on the basis of having no objective findings of OI.

This also deviates from the definition of OI in previous studies by the same authors. In fact, they have themselves shown that ME/CFS patients without hypotension or tachycardia but with OI symptoms have a marked reduction in cerebral blood flow on tilt-up testing, as do those with hypotension or tachycardia. [1]

[1] https://www.sciencedirect.com/science/article/pii/S2467981X20300044

Edit: I read too quickly, see @Hutan’s post below.

 

Apologies, I read too quickly. Thank you @Hutan.