E2 ModerateModerate confidencePEM not requiredCross-SectionalPeer-reviewedReviewed
Standard · 3 min
Patterns of orthostatic intolerance: the orthostatic tachycardia syndrome and adolescent chronic fatigue.
Stewart, J M, Gewitz, M H, Weldon, A et al. · The Journal of pediatrics · 1999 · DOI
Quick Summary
This study looked at how the hearts and blood pressure of adolescents with ME/CFS and a related condition called orthostatic tachycardia syndrome (OTS) respond when they stand up or are tilted upright. Researchers found that adolescents with ME/CFS had more severe problems with standing (like dizziness and fainting) than those with OTS, but the underlying patterns were quite similar. The study suggests that OTS may be a milder version of the same blood pressure and heart rate problems seen in ME/CFS.
Why It Matters
This study provides objective physiological evidence that ME/CFS and OTS share similar mechanisms of orthostatic intolerance—a common and disabling symptom for many ME/CFS patients. Understanding the continuum between these conditions may help researchers identify the underlying biological mechanisms and lead to better diagnostic tools and treatments for managing orthostatic symptoms in ME/CFS.
Observed Findings
All 25 adolescents with CFS experienced severe orthostatic symptoms during head-up tilt testing, compared to less severe symptoms in OTS patients.
16 of 23 CFS patients showed early orthostatic tachycardia (rapid heart rate response), with 13 of these also showing low blood pressure.
10 of 20 OTS patients showed early orthostatic tachycardia and 10 showed delayed tachycardia, both patterns resembling CFS but with lower frequency.
Acrocyanosis (blue discoloration of extremities) and edema (swelling) occurred in 18 of 25 CFS patients but in fewer OTS patients and only one simple faint patient.
Inferred Conclusions
Orthostatic intolerance in OTS may represent an attenuated or milder form of the physiological dysfunction seen in CFS.
The patterns of heart rate and blood pressure dysregulation overlap substantially between OTS and CFS, suggesting shared underlying pathophysiology.
CFS patients experience more severe orthostatic symptoms and more consistent physiological abnormalities than OTS patients, suggesting a spectrum of disease severity.
Remaining Questions
Do all OTS patients eventually develop CFS, or do these remain distinct conditions on a spectrum?
What are the cellular and neurological mechanisms causing the similar orthostatic patterns in both conditions?
What This Study Does Not Prove
This study does not prove that OTS causes CFS or vice versa, nor does it establish a causal mechanism linking them. The cross-sectional design shows correlation in physiological patterns but cannot determine whether OTS is truly a milder manifestation of the same disease or a distinct condition with overlapping features. Long-term follow-up studies would be needed to determine if patients with OTS progress to full CFS or remain stable.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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