Miwa, Kunihisa · Heart and vessels · 2016 · DOI
This study looked at how the hearts and nervous systems of 24 ME/CFS patients with orthostatic intolerance (dizziness or fatigue when standing) behaved on their "good days" versus "bad days." Researchers found that on bad days, patients' hearts raced more when standing up, they couldn't stand as long, and their hearts pumped less blood—suggesting their nervous systems were working abnormally, sometimes overactive and sometimes underactive.
Understanding how ME/CFS patients' autonomic nervous systems fluctuate between good and bad days could explain the characteristic symptom variability and inform better diagnostic criteria and treatment strategies. This research provides objective physiological evidence that orthostatic intolerance in ME/CFS involves complex, inconsistent autonomic dysfunction rather than a single fixed mechanism.
This study does not establish causation—only that physiological changes correlate with symptom severity days. The small sample size (n=24) and lack of a healthy control group limit generalizability. Self-identified "good" and "bad" days are subjective; this study cannot prove the observed differences cause symptom changes rather than reflect them.
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 →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Miwa, Kunihisa (2016). Variability of postural orthostatic tachycardia in patients with myalgic encephalomyelitis and orthostatic intolerance.. Heart and vessels. https://doi.org/10.1007/s00380-015-0744-3
BibTeX
@article{mecfsatlas-miwa-2016-variability-postural,
author = {Miwa, Kunihisa},
title = {Variability of postural orthostatic tachycardia in patients with myalgic encephalomyelitis and orthostatic intolerance.},
journal = {Heart and vessels},
year = {2016},
doi = {10.1007/s00380-015-0744-3},
note = {PubMed: 26374335},
url = {https://www.mecfsatlas.com/evidence/miwa-2016-variability-postural},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/miwa-2016-variability-postural
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