Miwa, Kunihisa · Heart and vessels · 2015 · DOI
This study looked at heart function in 40 ME/CFS patients compared to 40 healthy people. Researchers found that ME/CFS patients frequently had smaller hearts and difficulty standing up without dizziness or other symptoms (orthostatic intolerance). The smaller heart size appeared to pump less blood with each beat, which may explain why patients struggle with upright posture and fatigue.
Orthostatic intolerance is a major quality-of-life issue for ME/CFS patients, and this study provides objective cardiac evidence that may help explain this symptom. Understanding the structural and functional cardiac abnormalities in ME could guide targeted treatment strategies and validate the physical basis of the disease.
This study does not establish whether small heart size is a cause or consequence of ME/CFS, nor does it prove that cardiac dysfunction causes all ME/CFS symptoms. The cross-sectional design cannot determine whether cardiac changes precede symptom onset or develop afterward. The study also cannot explain the mechanism by which reduced cardiac output produces orthostatic intolerance in these patients.
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 (2015). Cardiac dysfunction and orthostatic intolerance in patients with myalgic encephalomyelitis and a small left ventricle.. Heart and vessels. https://doi.org/10.1007/s00380-014-0510-y
BibTeX
@article{mecfsatlas-miwa-2015-cardiac-dysfunction,
author = {Miwa, Kunihisa},
title = {Cardiac dysfunction and orthostatic intolerance in patients with myalgic encephalomyelitis and a small left ventricle.},
journal = {Heart and vessels},
year = {2015},
doi = {10.1007/s00380-014-0510-y},
note = {PubMed: 24736946},
url = {https://www.mecfsatlas.com/evidence/miwa-2015-cardiac-dysfunction},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-28. https://www.mecfsatlas.com/evidence/miwa-2015-cardiac-dysfunction
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