Its so unfortunate that heart research - published heart research that is - basically stopped completely in the US with the death of the CFS Cooperative Research Centers around 2001. This Japanese study suggests that a significant number of CFS patients are small hearted - not that they aren't good people - but that their hearts are smaller than expected as was their cardiac output. Both diastole and systole were reduced. I don't know why they think this might be happening. THis is the second study they've done that found this. Teitelbaum recommends fish oil to improve this: http://www.endfatigue.com/health_articles_f-n_2/Heart-fish_oil_improves_heart_function.html 1: J Cardiol. 2009 Aug;54(1):29-35. Epub 2009 Mar 28. Cardiac function fluctuates during exacerbation and remission in young adults with chronic fatigue syndrome and "small heart". Miwa K, Fujita M. Department of Internal Medicine, Nanto Family and Community Medical Center, 577 Matsubara, Nanto, Toyama 939-1518, Japan.