Chronic fatigue syndrome: illness severity, sedentary lifestyle, blood volume and evidence of diminished cardiac function.
Hurwitz, Barry E, Coryell, Virginia T, Parker, Meela et al. · Clinical science (London, England : 1979) · 2009 · DOI
Quick Summary
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.
Why It Matters
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.
Observed Findings
Severe ME/CFS participants had 10.2% lower cardiac volume (stroke index and end-diastolic volume) than healthy controls.
Severe ME/CFS participants had 25.1% lower cardiac contractility (velocity of circumferential shortening corrected by heart rate) than controls.
CFS subjects with TBV deficit (≥8% below ideal) showed mean deficits of −15.4% total blood volume, −13.2% plasma volume, and −19.1% red blood cell volume.
Total blood volume deficits explained 91–94% of group differences in cardiac volume indices.
No significant differences emerged in left ventricular mass index between groups despite cardiac volume differences.
Inferred Conclusions
Lower cardiac volume in severe ME/CFS is primarily a consequence of reduced total blood volume (hypovolemia) rather than impaired cardiac contractility.
Blood volume deficits represent a co-morbid physiological abnormality in ME/CFS that secondarily reduces cardiac chamber size.
Cardiac contractility impairment does not account for observed reductions in cardiac volume in ME/CFS patients.
The cardiac and blood volume alterations in ME/CFS warrant further investigation to determine their physiological significance and clinical implications.
Remaining Questions
What This Study Does Not Prove
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.
Tags
Symptom:Fatigue
Biomarker:Blood Biomarker
Phenotype:Severe
Method Flag:Exploratory OnlyStrong PhenotypingSevere ME Included
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 →