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https://www.medscape.com/viewarticle/911666
New Findings Elucidate Potentially Treatable Aspects of ME/CFS
This seems to be a very good article. What I found most fascinating (not least because it may apply to me! ) is where it talks about a 20% decrease in cerebral blood flow during a TTT, even without changes in BP and HR. I've only done a poor man's TTT - and I passed it. My BP and HR both stayed fine, no apparent problems, though I crashed the next day. But I always feel uneasy if I have to stand for any length of time over a few minutes and maybe this is why - this is fascinating stuff!
New Findings Elucidate Potentially Treatable Aspects of ME/CFS
Much of the focus on the clinical side centered around two key facets of the illness: postexertional malaise (PEM) and orthostatic intolerance (OI). According to the 2015 Institute (now Academy) of Medicine (IOM), definition of ME/CFS, PEM — described as a "crash" or worsening of all symptoms after even minor exertion — is required to make the diagnosis, along with at least 6 months of profound and disabling fatigue, and unrefreshing sleep. A fourth criterion is either OI or cognitive dysfunction.
David M. Systrom, MD, a pulmonary and critical care medicine specialist and director of the Invasive Cardiopulmonary Laboratory at Brigham and Women’s Hospital (BWH), Boston, described results from invasive cardiopulmonary testing that show that patients with ME/CFS have distinct defects in both ventricular filling pressure and oxygen extraction from the muscles.
Neither of those are features of deconditioning, in which the major defect is decreased stroke volume and cardiac output. In ME/CFS patients, he found supranormal pulmonary blood flow compared with VO2 max, indicating left-to-right shunting.
In addition, Systrom found that a large proportion of ME/CFS patients with these cardiopulmonary defects also have biopsy-demonstrated small fiber polyneuropathy, suggesting that PEM may be due to an underlying autonomic nervous system dysfunction.
Also at the meeting, Peter C. Rowe, MD, director of the Children's Center Chronic Fatigue Clinic and professor of pediatrics at Johns Hopkins University School of Medicine, Baltimore, presented his colleagues' findings showing that, in patients with ME/CFS who have OI, cerebral blood flow drops significantly compared with controls on tilt-table testing even without changes in heart rate or blood pressure. And this was true regardless of VO2 max or recorded steps, suggesting again that the phenomenon isn't simply due to illness-related inactivity.
Two phenomena appear to be contributing to the OI simultaneously, Rowe said: increased pooling of blood in the legs and decreased vasoconstriction, along with a decrease in circulating blood volume.
But in a new and potentially paradigm-shifting finding, van Campen and colleagues used transcranial Doppler echography of the internal carotid and vertebral arteries during the tilt-table test in over 400 ME/CFS patients. They displayed a greater than 20% reduction in cerebral blood flow compared with a 6% reduction found previously in healthy volunteers
"It was quite a profound change," Rowe said, noting, "Maybe we've been looking in the wrong place. If symptoms are due to decreasing cerebral blood flow, maybe that's where we should focus."
The finding was seen even among the patients who did not demonstrate heart rate and blood pressure changes during the tilt test.
This seems to be a very good article. What I found most fascinating (not least because it may apply to me! ) is where it talks about a 20% decrease in cerebral blood flow during a TTT, even without changes in BP and HR. I've only done a poor man's TTT - and I passed it. My BP and HR both stayed fine, no apparent problems, though I crashed the next day. But I always feel uneasy if I have to stand for any length of time over a few minutes and maybe this is why - this is fascinating stuff!