Hurwitz, Barry E, Coryell, Virginia T, Parker, Meela et al. · Clinical science (London, England : 1979) · 2009 · DOI
This study found that people with severe ME/CFS have smaller hearts and significantly less blood volume compared to healthy controls. The reduced heart size appears to be caused by having less blood circulating in their bodies, not by weak heart muscle. The researchers suggest this blood volume deficit—a condition where the body has less circulating blood than normal—may be an important factor in ME/CFS symptoms.
This study provides objective physiological evidence of blood volume abnormalities in ME/CFS, suggesting a measurable biological mechanism underlying cardiac symptoms. Understanding that reduced heart size may result from insufficient blood volume rather than heart muscle weakness could guide future diagnostic approaches and treatment strategies for ME/CFS patients experiencing cardiac symptoms and exercise intolerance.
This study does not establish causation—it cannot determine whether blood volume deficits cause ME/CFS symptoms or result from the disease process. The cross-sectional design captures only a single time point and cannot demonstrate whether these cardiac and blood volume changes precede illness onset or evolve over time. The study also does not clarify the clinical significance of these findings or whether addressing blood volume could improve patient outcomes.
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
Hurwitz, Barry E, Coryell, Virginia T, Parker, Meela, Martin, Pedro, Laperriere, Arthur, Klimas, Nancy G, et al. (2009). Chronic fatigue syndrome: illness severity, sedentary lifestyle, blood volume and evidence of diminished cardiac function.. Clinical science (London, England : 1979). https://doi.org/10.1042/CS20090055
BibTeX
@article{mecfsatlas-hurwitz-2009-chronic-fatigue,
author = {Hurwitz, Barry E and Coryell, Virginia T and Parker, Meela and Martin, Pedro and Laperriere, Arthur and Klimas, Nancy G and Sfakianakis, George N and Bilsker, Martin S},
title = {Chronic fatigue syndrome: illness severity, sedentary lifestyle, blood volume and evidence of diminished cardiac function.},
journal = {Clinical science (London, England : 1979)},
year = {2009},
doi = {10.1042/CS20090055},
note = {PubMed: 19469714},
url = {https://www.mecfsatlas.com/evidence/hurwitz-2009-chronic-fatigue},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-27. https://www.mecfsatlas.com/evidence/hurwitz-2009-chronic-fatigue
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