Khan, Muhammad Shahzeb, Miller, Amanda J, Ejaz, Arooba et al. · Journal of the American Heart Association · 2025 · DOI
When you stand up, your body normally adjusts blood flow to keep your brain supplied with oxygen. Some people have problems with this adjustment, causing dizziness, fatigue, or fainting—a condition called orthostatic intolerance. This review explains that many ME/CFS and long COVID patients have reduced blood flow to the brain when standing, even though their heart rate and blood pressure look normal on standard tests. The authors review different tools doctors can use to actually measure brain blood flow, rather than just relying on heart rate and blood pressure readings.
This review directly addresses a critical diagnostic gap in ME/CFS: many patients have real brain blood flow problems that go undetected because standard vital sign monitoring appears normal. By highlighting the inadequacy of heart rate and blood pressure as sole markers of cerebral perfusion in ME/CFS, this work validates patient experiences of disabling symptoms and advocates for better measurement tools. Improved CBF assessment could lead to more accurate diagnoses, better understanding of disease mechanisms, and targeted treatments for ME/CFS patients with orthostatic intolerance.
This review does not establish the prevalence of CBF dysfunction in ME/CFS populations or prove that specific measurement techniques are superior to others in clinical practice. It does not provide original data on ME/CFS patients themselves but rather synthesizes existing literature across multiple OI syndromes. The review cannot establish causality between CBF abnormalities and ME/CFS symptoms—only that these phenomena co-occur and warrant investigation with better measurement tools.
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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