A recent fascinating study suggested that the diastolic dysfunction that Dr. Cheney is finding and the low stroke volume output that others have found may not be due to some sort of energetic problem but simply to the fact that CFS patients don't have normal amounts of blood in their systems. once the investigators statistically accounted for the low blood volume in the CFS patients the other cardiac issues disappeared. http://www.ncbi.nlm.nih.gov/pubmed/19469714?ordinalpos=28&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum The befuddling thing here is that correcting blood volume in most CFS patients does not fix their symptoms! If this study is correct then the heart issues Dr. Cheney is focusing on may be secondary to other issues. Still the fact that low blood volume has now been shown to be present in CFS patients several studies does give researchers a clue. It is after all an unusual symptom - well it may not cause CFS it's possible that whatever is causing low blood volume - could cause or at least contribute to CFS.