RE: Cheney/Peckerman/Sinatra's theory on heart function in relation to CFS Testing was an easy process. The most difficult part of the test was getting to the doctor's office and then getting back home again! My test results seem to hang mostly in the low side of normal. A few results were below normal and a few were above normal. My cardiac output was 4.7 while lying down and 4.0 when standing up. These numbers are just inside the "normal" range. They are normal, but very low normal. I am not totally clear on what all of these measurements mean (there are 18 measurements that are taken by the BioZ machine). The cardiologist explained my test results by using the analogy of a super-charged car engine and a little 4-cylinder sub-compact engine. The cardiologist said that I have a low-powered engine instead of a high-powered engine. He did not seem to think that these low numbers were any big deal. He did not recommend any treatment. I have found some additional information regarding these tests at impedancecardiography.com which provides a descriptive overview of the test. Also, there is an article by Neil Treister titled "A Clinician's Guide to Interpreting an Impedance Cardiography Hemodynamic Status Report" that provides some more technical explanations. The cardiologist did decide that he wants me to take another test. I am scheduled for a Stress Echo on Monday the 22nd. I seriously doubt that the Stress Echo will show anything more than my mitral valve prolapse, but if something interesting turns up, I will post it on this message board!