Miwa, Kunihisa, Fujita, Masatoshi · Journal of cardiology · 2009 · DOI
This study looked at the hearts of 42 young adults with ME/CFS and found that 62% had unusually small hearts on chest X-rays. Using heart ultrasound scans, researchers discovered these patients had smaller heart chambers and weaker heart function compared to healthy controls. Importantly, when patients improved, their heart size and function got better, suggesting the heart changes are connected to symptom severity rather than permanent damage.
This research provides objective cardiac evidence for a physical basis of ME/CFS symptoms, moving beyond purely subjective measures. The direct correlation between cardiac functional changes and symptom severity suggests that cardiac assessment may be valuable for monitoring disease progression and response to treatment in ME/CFS patients.
This study does not prove that small heart syndrome causes ME/CFS—it demonstrates association, not causation. The small longitudinal cohort (10 patients followed) and lack of control group in the follow-up phase limit generalizability. The study cannot rule out whether cardiac changes are primary pathology or secondary consequences of reduced activity and deconditioning.
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 & Fujita, Masatoshi (2009). Cardiac function fluctuates during exacerbation and remission in young adults with chronic fatigue syndrome and "small heart".. Journal of cardiology. https://doi.org/10.1016/j.jjcc.2009.02.008
BibTeX
@article{mecfsatlas-miwa-2009-cardiac-function,
author = {Miwa, Kunihisa and Fujita, Masatoshi},
title = {Cardiac function fluctuates during exacerbation and remission in young adults with chronic fatigue syndrome and "small heart".},
journal = {Journal of cardiology},
year = {2009},
doi = {10.1016/j.jjcc.2009.02.008},
note = {PubMed: 19632517},
url = {https://www.mecfsatlas.com/evidence/miwa-2009-cardiac-function},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/miwa-2009-cardiac-function
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