Miwa, Kunihisa, Fujita, Masatoshi · Clinical cardiology · 2008 · DOI
This study found that people with ME/CFS are more likely to have a smaller heart than healthy people. Researchers used chest X-rays and heart ultrasounds to measure heart size in 56 ME/CFS patients under age 50 and compared them to 38 healthy controls. Patients with both ME/CFS and a small heart also experienced more symptoms like dizziness when standing, cold feet, and heart rhythm irregularities.
This study identifies a potential structural cardiac abnormality in a majority of younger ME/CFS patients that may contribute to fatigue and orthostatic symptoms. Understanding small heart syndrome could help explain why ME/CFS patients experience disproportionate fatigue with exertion and may guide future therapeutic approaches targeting cardiac function.
This study does not prove that small heart syndrome causes ME/CFS, only that the two conditions co-occur more frequently than expected. The cross-sectional design prevents determination of temporal relationships—small heart could be a consequence of ME/CFS rather than a predisposing factor. The study cannot establish whether treating small heart syndrome would improve ME/CFS symptoms.
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 (2008). Small heart syndrome in patients with chronic fatigue syndrome.. Clinical cardiology. https://doi.org/10.1002/clc.20227
BibTeX
@article{mecfsatlas-miwa-2008-small-heart,
author = {Miwa, Kunihisa and Fujita, Masatoshi},
title = {Small heart syndrome in patients with chronic fatigue syndrome.},
journal = {Clinical cardiology},
year = {2008},
doi = {10.1002/clc.20227},
note = {PubMed: 18636530},
url = {https://www.mecfsatlas.com/evidence/miwa-2008-small-heart},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/miwa-2008-small-heart
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