This is research conducted by Julia Newton and others and published in the BMJ.
http://openheart.bmj.com/content/3/1/e000381.longConclusions This study confirms an association between reduced cardiac
volumes and blood volume in CFS. Lack of relationship between length
of disease, cardiac and plasma volumes suggests findings are not
secondary to deconditioning. The relationship between plasma volume
and severity of fatigue symptoms suggests a potential therapeutic
target in CFS.